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Kivy Anchor and gridlayout centering
Question: I am using anchor layout to hold widgets, my widget is a gridlayout, the issue
is, I want a compact login display UI, however, I am getting 3 contorls near,
and logout button at end, all are not together (should not have much spacing)
and should be centered in Anchor Layout.
I am getting it as which is not looking good: 
Codes are as follows:
**main**.py:
from kivy.app import App
from formcontrol import FormControl
class MyApp(App):
def build(self):
self.title="sample App"
self.formcontrol = FormControl()
return self.formcontrol
if __name__ == '__main__':
MyApp().run()
FormControl.py:
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.anchorlayout import AnchorLayout
from login.logincodes import LoginControl
from login.logincodes import AfterLogin
class FormControl(AnchorLayout):
'''
classdocs
'''
def __init__(self, **kwargs):
'''
Constructor
'''
super(FormControl,self).__init__(**kwargs)
c= LoginControl()
c.setparent(self)
self.add_widget(c)
def changewidget(self,to):
if to == 'AfterLogin':
self.clear_widgets()
self.add_widget(AfterLogin())
logincodes.py:
from kivy.uix.gridlayout import GridLayout
class LoginControl(GridLayout):
_parentwidget=None
def __init__(self, **kwargs):
super(LoginControl,self).__init__(**kwargs)
self.userid.text='Welcome'
def setparent(self,parent):
self._parentwidget=parent
def changewidget(self,to):
self._parentwidget.changewidget(to)
def login_pressed(self,button):
print(button.text)
print(self.userid.text)
print(self.userpw.text)
self.changewidget('AfterLogin')
def close_pressed(self,button):
print(button.text)
exit()
class AfterLogin(GridLayout):
def __init__(self,**kwargs):
super(AfterLogin,self).__init__(**kwargs)
my.ky file:
<LoginControl>:
rows: 3
cols: 1
userid: userid
userpw: userpw
BoxLayout:
size_hint_y: None
height: '32dp'
Label:
text: 'User ID'
TextInput:
id: userid
text: 'some password'
BoxLayout:
size_hint_y: None
height: '32dp'
Label:
text: 'Password'
TextInput:
id: userpw
password: True
text: 'some password'
Button:
text: 'Login'
on_press: root.login_pressed(self)
size_hint_y: None
height: '32dp'
Button:
text: 'Close'
on_press: root.close_pressed(self)
size_hint_y: None
height: '32dp'
<AfterLogin>:
rows: 1
Label:
text: 'Logged In'
Please make me learn where I went wrong in configuring the UI and I dont want
to use a float layout which is like using points to place widgets. I am new to
both Python and Kivy. Your support and advices are valuable to me to improve,
Answer: On your `GridLayout` you specify `rows` = 3 and `cols` = 1, which means the
layout has space for 3 children. When it gets to laying out the Close button,
all the rows and cols have been used up so the Close button goes to the
default position `(0, 0)`. I would just specify `cols` and leave `rows` out -
it will use as many rows as necessary to lay out the children.
Second, this isn't a problem, but there's a quicker way to set all of the
children's height to 32dp. Rather than specifying `size_hint` and `height` on
all of the children, you can instead set `row_default_height` and
`row_force_default` on the `GridLayout`.
Finally, your `GridLayout` is still taking up all the space, which is why it's
not centering in the `AnchorLayout`. This is easily solved with a `GridLayout`
due to the `minimum_height` property - set `height` to `minimum_height` and
`size_hint_y` to `None`, and it will center.
Putting it all together:
<LoginControl>:
cols: 1
row_force_default: True
row_default_height: '32dp'
size_hint_y: None
height: self.minimum_height
|
Minidom getElementById not working
Question: Minidom's getElementById function is returning None for any entry I pass to
it.
For example, this code:
l = minidom.parseString('<node id="node">Node</node>')
print(l.getElementById("node"))
Prints "None" on my computer.
I must be doing something here wrong but I can't figure it out!
I'm running Python 3.3.2 if that helps.
Answer: If you want to get elements with name="node"
l.getElementsByTagName("node")
If you want to get elements with attribute having an attribute "id" with value
"node", use [xpath](https://code.google.com/p/py-dom-xpath/):
import xpath
xpath.find("//*['id=node']",l) #search for all elements with an attribute id="node"
|
Python - Read TXT File lines --> Array
Question: I need to open a text file with Python and read this Text file line by line to
put it into an arrary. Later on I want to write every single content from that
array into a database. This is my code so far:
#!/usr/bin/python
# -*- coding: utf8 -*-
#importieren der Module
import MySQLdb
import sys
import re # regex
import codecs # utf8 support
# Datei file einlesen
names = []
fo = open("file.txt", "r")
print "Name of file:", fo.name
for line in fo:
line = line.strip()
fo.close()
How can I do this ? What is the right command to insert the text lines into an
array ?
Answer: If I'm understanding you correctly, your text file looks something like this:
E YD6567 E YD9876 E YD9867 etc...
And you wish to remove the "E " and just store the "YD####" in a list. Your
loop will look like this:
for line in fo:
names.append(line.replace('E ', '')
The "append" function adds an item to a list. The "replace" function replaces
whatever part of the string you specify with whatever else you specify (in
this case, replacing "E " with nothing, effectively removing it from the
string).
If you would like to store the full line (including "E "), it's as simple as:
for line in fo:
names.append(line)
|
accurate image aspect ratio in python
Question: I have the following code to get the aspect ratio of an image
img0 = color.rgb2gray(io.imread("C:\\work\\TRAIN\\SET1\\bus.jpg"))
img0 = resize(img0, (40, 116))
ar = 1.0 * (img0.shape[1]/img0.shape[0])
print "aspect ratio: "
print ar
The output is `2.0`. But that's not true. For an image with width 116 and
height 40, the aspect ratio should be `116/40 = 2.9`.
Where is my calculation going wrong?
Answer: The problem in you case is that img0.shape[1] and img0.shape[0] are both
integers. You have performed integer division, and then converted it to float.
You could try:
float(img0.shape[1]) / img0.shape[0]
or
1.0 * img0.shape[1] / img0.shape[0]
or, my recommended method, is to add as the first line of code in the file
this import
from __future__ import division
This will make "/" always perform floating point calculation, to avoid such
cases. If you want to specifically use integer division, use "//", as in 10 //
3
|
Py2neo Neo4j Batch submit error
Question: I have a json file with data of around 1.4 million nodes and I wanted to
construct a Neo4j graph database for that. I tried to use py2neo's batch
submit function. My code is as follows:
# the variable words is a list containing node names
from py2neo import neo4j
batch = neo4j.WriteBatch(graph_db)
nodedict = {}
# I decided to use a dictionary because I would be creating relationships
# by referring to the dictionary entries later
for i in words:
nodedict[i] = batch.create({"name":i})
results = batch.submit()
The error shown is as follows:
Traceback (most recent call last):
File "test.py", line 36, in <module>
results = batch.submit()
File "/usr/lib/python2.6/site-packages/py2neo/neo4j.py", line 2116, in submit
for response in self._submit()
File "/usr/lib/python2.6/site-packages/py2neo/neo4j.py", line 2085, in _submit
for id_, request in enumerate(self.requests)
File "/usr/lib/python2.6/site-packages/py2neo/rest.py", line 427, in _send
return self._client().send(request)
File "/usr/lib/python2.6/site-packages/py2neo/rest.py", line 364, in send
return Response(request.graph_db, rs.status, request.uri, rs.getheader("Loc$
File "/usr/lib/python2.6/site-packages/py2neo/rest.py", line 278, in __init__
raise SystemError(body)
SystemError: None
Can anybody please tell me what exactly is happening here? Does it have
anything to do with the fact that the batch query is pretty large? If so, what
can be done? Thanks in advance! :)
Answer: So here's what I figured out (Thanks to this question: [py2neo - Neo4j -
System Error - Create Batch
Nodes/Relationships](http://stackoverflow.com/questions/17902741/py2neo-
neo4j-system-error-create-batch-nodes-relationships)):
The py2neo batch submit function has it's own limitations in terms of queries
that can be made. While, I wasn't able to get a exact amount on the upper
limit, I tried to limit my number of queries per batch to 5000. So I decided
to run the following piece of code:
# the variable words is a list containing node names
from py2neo import neo4j
batch = neo4j.WriteBatch(graph_db)
nodedict = {}
# I decided to use a dictionary because I would be creating relationships
# by referring to the dictionary entries later
for index, i in enumerate(words):
nodedict[i] = batch.create({"name":i})
if index%5000 == 0:
batch.submit()
batch = neo4j.WriteBatch(graph_db) # As stated by Nigel below, I'm creating a new batch
batch.submit() #for the final batch
This way, I sent batch requests (of size 5k queries) and was successfully able
to get my entire graph created!
|
Split streaming message in multiple Dicts
Question: I'm trying to use json to decode a streaming message but throws the following
ValueError:
File "/usr/lib/python2.7/json/__init__.py", line 338, in loads
return _default_decoder.decode(s)
File "/usr/lib/python2.7/json/decoder.py", line 369, in decode
raise ValueError(errmsg("Extra data", s, end, len(s)))
ValueError: Extra data: line 2 column 1 - line 23571 column 1 (char 126 - 72358378)
I searched in SO and the possible reason is my streaming message. If so, How
can split my streaming message into multiple dicts in a pythonic way?
some lines of my streaming message:
{"delete":{"status":{"id":486174602859528192,"id_str":"486174602859528192","user_id":2455171405,"user_id_str":"2455171405"}}}
{"delete":{"status":{"id":244223991382937601,"id_str":"244223991382937601","user_id":236405781,"user_id_str":"236405781"}}}
{"delete":{"status":{"id":243934303371792384,"id_str":"243934303371792384","user_id":236405781,"user_id_str":"236405781"}}}
{"delete":{"status":{"id":320790822129913856,"id_str":"320790822129913856","user_id":320634758,"user_id_str":"320634758"}}}
{"delete":{"status":{"id":399494495630155776,"id_str":"399494495630155776","user_id":1227287820,"user_id_str":"1227287820"}}}
{"delete":{"status":{"id":399528981206007808,"id_str":"399528981206007808","user_id":1227287820,"user_id_str":"1227287820"}}}
{"created_at":"Wed Jul 09 12:16:27 +0000 2014","id":486846341600251904,"id_str":"486846341600251904","text":"#RT \u0430 \u0437\u043d\u0430\u0435\u0442\u0435 \u043f\u043e\u0447\u0435\u043c\u0443 \u044f \u043d\u0435 \u0431\u0443\u0434\u0443 \u043f\u043e\u0434\u0434\u0435\u0440\u0436\u0438\u0432\u0430\u0442\u044c \u0442\u0440\u0435\u043d\u0434 \u043e \u041d\u0438\u043a\u043e\u043b\u044c?","source":"\u003ca href=\"http:\/\/www.ckhi.com.ua\" rel=\"nofollow\"\u003e\"Original atok\"\u003c\/a\u003e","truncated":false,"in_reply_to_status_id":null,"in_reply_to_status_id_str":null,"in_reply_to_user_id":null,"in_reply_to_user_id_str":null,"in_reply_to_screen_name":null,"user":{"id":2530930573,"id_str":"2530930573","name":"\u041b\u0435\u043f\u0430\u0448\u0438\u043da \u041f\u0435\u043b\u0430\u0433\u0435\u044f","screen_name":"miki4390","location":"\u0421\u0430\u043d\u043a\u0442-\u041f\u0435\u0442\u0435\u0440\u0431\u0443\u0440\u0433","url":"https:\/\/twitter.com\/miki4390","description":"\u042f-\u0442\u043e \u0442\u0435\u0440\u043f\u043b\u044e. \u041d\u043e \u0442\u044b-\u0442\u043e \u043f\u043e\u0436\u0430\u043b\u0435\u0435\u0448\u044c...","protected":false,"verified":false,"followers_count":0,"friends_count":0,"listed_count":0,"favourites_count":0,"statuses_count":11,"created_at":"Wed May 28 21:41:41 +0000 2014","utc_offset":null,"time_zone":null,"geo_enabled":false,"lang":"en","contributors_enabled":false,"is_translator":false,"profile_background_color":"C0DEED","profile_background_image_url":"http:\/\/abs.twimg.com\/images\/themes\/theme1\/bg.png","profile_background_image_url_https":"https:\/\/abs.twimg.com\/images\/themes\/theme1\/bg.png","profile_background_tile":false,"profile_link_color":"0084B4","profile_sidebar_border_color":"C0DEED","profile_sidebar_fill_color":"DDEEF6","profile_text_color":"333333","profile_use_background_image":true,"profile_image_url":"http:\/\/abs.twimg.com\/sticky\/default_profile_images\/default_profile_3_normal.png","profile_image_url_https":"https:\/\/abs.twimg.com\/sticky\/default_profile_images\/default_profile_3_normal.png","profile_banner_url":"https:\/\/pbs.twimg.com\/profile_banners\/2530930573\/1404903710","default_profile":true,"default_profile_image":true,"following":null,"follow_request_sent":null,"notifications":null},"geo":null,"coordinates":null,"place":null,"contributors":null,"retweet_count":0,"favorite_count":0,"entities":{"hashtags":[{"text":"RT","indices":[0,3]}],"trends":[],"urls":[],"user_mentions":[],"symbols":[]},"favorited":false,"retweeted":false,"possibly_sensitive":false,"filter_level":"medium","lang":"ru"}
{"delete":{"status":{"id":295365152621080577,"id_str":"295365152621080577","user_id":710752640,"user_id_str":"710752640"}}}
Answer: Your JSON is in fact set of JSON lines.
# Decoding JSON line by line
Reading all the lines at once results in broken JSON data.
Reading the lines one by one and decoding works well.
With your json lines in file "jslines.json" following code:
>>> import json
>>> fname = "jslines.json"
>>> f = open(fname)
>>> for line in f:
... print json.loads(line)
decodes and prints all the lines.
# Building valid JSON array from lines
Alternative approach is to use the lines to build valid JSON structure, in
this case an array. We have to get list of the lines (as text), concatenate
using ",", and enclose between "[" and "]"".
>>> with open(fname) as f:
... lines = list(f)
Now we have all the lines in a list `lines`
Build the resulting JSON text:
>>> jstext = "[" + ",".join(lines) + "]"
And load it into dictionary:
>>> json.loads(jstext)
This works with the data you have provided.
|
Python Matplotlib animation frames are overlapping
Question: I am working on my orbit program, and I have currently only animated the moon
with a downward (-y) velocity of -1023. The animation works, but each frame
stays on the figure when the next one comes on: 
Here is my code:
import numpy as np
import matplotlib.pyplot as plt
import math
import matplotlib.animation as animation
er = 6378100*10#m #earth radius
mr = 1737400*10#m #moon radius
em = 5.97219*10**24#kg #earth mass
mm = 7.34767309*10**22#kg #moon mass
d = 384400000#m #distance earth-moon
G = 6.67384*10**(-11) #gravity constant
mv = -1023#m/s #Moon velocity
nts = 10000 #no. time steps
def circle(r, h, k, a):
x = r*math.cos(a)+h
y = r*math.sin(a)+k
plt.scatter(x,y)
def simData():
tmax = 10000*nts
ts = 10000
x = 0.0
t = 0.0
while t < tmax:
n = 0
for i in range(120):
circle(mr, d, mv*t, n)
n = n + math.pi/60
t = t + ts
yield x, t
def simPoints(simData):
x, t = simData[0], simData[1]
time_text.set_text(time_template%(t))
line.set_data(t, x)
return line, time_text
fig = plt.figure()
ax = plt.axes(xlim=(-430000000, 430000000), ylim=(-430000000, 430000000))
line, = ax.plot([], [], 'bo', ms=10)
time_template = 'Time = %.1f s' # prints running simulation time
time_text = ax.text(0.05, 0.9, '', transform=ax.transAxes)
ani = animation.FuncAnimation(fig, simPoints, simData, blit=False,\
interval=10, repeat=True)
plt.show()
Answer: The answer is simple: `matplotlib` animation does not wipe the image between
frames. The point is that you yourself have to change the properties of the
objects on the screen. Now you instead plot a new image with some new objects
when you do the `plt.scatter` in `circle`.
I changed a few lines in your code to avoid adding new objects, see the
comment lines marked with `####`. Now it should be a bit snappier. (Even
though the Moon is escaping Earth's gravitational field. Pity.)
import numpy as np
import matplotlib.pyplot as plt
import math
import matplotlib.animation as animation
er = 6378100*10#m #earth radius
mr = 1737400*10#m #moon radius
em = 5.97219*10**24#kg #earth mass
mm = 7.34767309*10**22#kg #moon mass
d = 384400000#m #distance earth-moon
G = 6.67384*10**(-11) #gravity constant
mv = -1023#m/s #Moon velocity
nts = 10000 #no. time steps
def circle(r, h, k, a):
x = r*math.cos(a)+h
y = r*math.sin(a)+k
#### CHANGED
moony.center = x,y
def simData():
tmax = 10000*nts
ts = 10000
x = 0.0
t = 0.0
while t < tmax:
n = 0
for i in range(120):
circle(mr, d, mv*t, n)
n = n + math.pi/60
t = t + ts
yield x, t
def simPoints(simData):
x, t = simData[0], simData[1]
time_text.set_text(time_template%(t))
line.set_data(t, x)
return line, time_text
fig = plt.figure()
ax = plt.axes(xlim=(-430000000, 430000000), ylim=(-430000000, 430000000))
#### CHANGED: a grey circle of moony dimensions to be moved around
moony = plt.Circle((0,0), mr, facecolor=(.8,.8,.8))
ax.add_artist(moony)
time_template = 'Time = %.1f s' # prints running simulation time
time_text = ax.text(0.05, 0.9, '', transform=ax.transAxes)
ani = animation.FuncAnimation(fig, simPoints, simData, blit=False,\
interval=10, repeat=True)
plt.show()
Of course, you'll probably want to create a circle to illustrate Earth, as
well. You do not need to have any `plt.plot` commands in the file if you just
want to plot two objects.
|
Code to check if an object is a list of lists python
Question: I was review how to check if something is a list of lists from here [List of
Lists check](http://stackoverflow.com/questions/5251663/determine-if-a-list-
contains-other-lists).
But When I use the code, it appears to fail. It should not print 'asdf' in
this case since `lst` is a list of strings. What am I doing wrong?
` lst = wikiinfo_df.Data.ix[2]
print lst
OUT:
['NYSE', ': ', 'GS', '\n', 'Dow Jones Industrial Average Component', '\n', 'S&P 500 Component']
if all(isinstance(i, list) for i in lst):
print 'asdf'
OUT:
asdf
UPDATE - output of print `__builtins__` and `dir(__builtins__)`, pandas
versions, all module
print numpy.core.fromnumeric
numpy.core.fromnumeric
pandas: 0.12.0
python: 2.7.5 |Anaconda 1.8.0 (x86_64)| (default, Oct 24 2013, 07:02:20) [GCC 4.0.1 (Apple Inc. build 5493)]
{'bytearray': <type 'bytearray'>, 'IndexError': <type 'exceptions.IndexError'>, 'all': <built-in function all>, 'help': Type help() for interactive help, or help(object) for help about object., 'vars': <built-in function vars>, 'SyntaxError': <type 'exceptions.SyntaxError'>, '__IPYTHON__active': 'Deprecated, check for __IPYTHON__', 'unicode': <type 'unicode'>, 'UnicodeDecodeError': <type 'exceptions.UnicodeDecodeError'>, 'memoryview': <type 'memoryview'>, 'isinstance': <built-in function isinstance>, 'copyright': Copyright (c) 2001-2013 Python Software Foundation.
All Rights Reserved.
Copyright (c) 2000 BeOpen.com.
All Rights Reserved.
Copyright (c) 1995-2001 Corporation for National Research Initiatives.
All Rights Reserved.
Copyright (c) 1991-1995 Stichting Mathematisch Centrum, Amsterdam.
All Rights Reserved., 'NameError': <type 'exceptions.NameError'>, 'BytesWarning': <type 'exceptions.BytesWarning'>, 'dict': <type 'dict'>, 'input': <function <lambda> at 0x12c3adb90>, 'oct': <built-in function oct>, 'bin': <built-in function bin>, 'SystemExit': <type 'exceptions.SystemExit'>, 'StandardError': <type 'exceptions.StandardError'>, 'format': <built-in function format>, 'repr': <built-in function repr>, 'sorted': <built-in function sorted>, 'False': False, 'RuntimeWarning': <type 'exceptions.RuntimeWarning'>, 'list': <type 'list'>, 'iter': <built-in function iter>, 'reload': <built-in function reload>, 'Warning': <type 'exceptions.Warning'>, '__package__': None, 'round': <built-in function round>, 'dir': <built-in function dir>, 'cmp': <built-in function cmp>, 'set': <type 'set'>, 'bytes': <type 'str'>, 'reduce': <built-in function reduce>, 'intern': <built-in function intern>, 'issubclass': <built-in function issubclass>, 'Ellipsis': Ellipsis, 'EOFError': <type 'exceptions.EOFError'>, 'locals': <built-in function locals>, 'BufferError': <type 'exceptions.BufferError'>, 'slice': <type 'slice'>, 'FloatingPointError': <type 'exceptions.FloatingPointError'>, 'sum': <built-in function sum>, 'getattr': <built-in function getattr>, 'abs': <built-in function abs>, 'print': <built-in function print>, 'True': True, 'FutureWarning': <type 'exceptions.FutureWarning'>, 'ImportWarning': <type 'exceptions.ImportWarning'>, 'None': None, 'hash': <built-in function hash>, 'ReferenceError': <type 'exceptions.ReferenceError'>, 'len': <built-in function len>, 'credits': Thanks to CWI, CNRI, BeOpen.com, Zope Corporation and a cast of thousands
for supporting Python development. See www.python.org for more information., 'frozenset': <type 'frozenset'>, '__name__': '__builtin__', 'ord': <built-in function ord>, 'super': <type 'super'>, 'TypeError': <type 'exceptions.TypeError'>, 'license': Type license() to see the full license text, 'KeyboardInterrupt': <type 'exceptions.KeyboardInterrupt'>, 'UserWarning': <type 'exceptions.UserWarning'>, 'filter': <built-in function filter>, 'range': <built-in function range>, 'staticmethod': <type 'staticmethod'>, 'SystemError': <type 'exceptions.SystemError'>, 'BaseException': <type 'exceptions.BaseException'>, 'pow': <built-in function pow>, 'RuntimeError': <type 'exceptions.RuntimeError'>, 'float': <type 'float'>, 'MemoryError': <type 'exceptions.MemoryError'>, 'StopIteration': <type 'exceptions.StopIteration'>, 'globals': <built-in function globals>, 'divmod': <built-in function divmod>, 'enumerate': <type 'enumerate'>, 'apply': <built-in function apply>, 'LookupError': <type 'exceptions.LookupError'>, 'open': <built-in function open>, 'basestring': <type 'basestring'>, 'UnicodeError': <type 'exceptions.UnicodeError'>, 'zip': <built-in function zip>, 'hex': <built-in function hex>, 'long': <type 'long'>, 'next': <built-in function next>, 'ImportError': <type 'exceptions.ImportError'>, 'chr': <built-in function chr>, 'xrange': <type 'xrange'>, 'type': <type 'type'>, '__doc__': "Built-in functions, exceptions, and other objects.\n\nNoteworthy: None is the `nil' object; Ellipsis represents `...' in slices.", 'Exception': <type 'exceptions.Exception'>, '__IPYTHON__': True, 'tuple': <type 'tuple'>, 'UnicodeTranslateError': <type 'exceptions.UnicodeTranslateError'>, 'reversed': <type 'reversed'>, 'UnicodeEncodeError': <type 'exceptions.UnicodeEncodeError'>, 'IOError': <type 'exceptions.IOError'>, 'hasattr': <built-in function hasattr>, 'delattr': <built-in function delattr>, 'setattr': <built-in function setattr>, 'raw_input': <function <lambda> at 0x12c3ad230>, 'SyntaxWarning': <type 'exceptions.SyntaxWarning'>, 'compile': <built-in function compile>, 'ArithmeticError': <type 'exceptions.ArithmeticError'>, 'str': <type 'str'>, 'property': <type 'property'>, 'dreload': <function reload at 0x1022b8c08>, 'GeneratorExit': <type 'exceptions.GeneratorExit'>, 'int': <type 'int'>, '__import__': <built-in function __import__>, 'KeyError': <type 'exceptions.KeyError'>, 'coerce': <built-in function coerce>, 'PendingDeprecationWarning': <type 'exceptions.PendingDeprecationWarning'>, 'file': <type 'file'>, 'EnvironmentError': <type 'exceptions.EnvironmentError'>, 'unichr': <built-in function unichr>, 'id': <built-in function id>, 'OSError': <type 'exceptions.OSError'>, 'DeprecationWarning': <type 'exceptions.DeprecationWarning'>, 'min': <built-in function min>, 'UnicodeWarning': <type 'exceptions.UnicodeWarning'>, 'execfile': <built-in function execfile>, 'any': <built-in function any>, 'complex': <type 'complex'>, 'bool': <type 'bool'>, 'get_ipython': <bound method ZMQInteractiveShell.get_ipython of <IPython.kernel.zmq.zmqshell.ZMQInteractiveShell object at 0x1022b9dd0>>, 'ValueError': <type 'exceptions.ValueError'>, 'NotImplemented': NotImplemented, 'map': <built-in function map>, 'buffer': <type 'buffer'>, 'max': <built-in function max>, 'object': <type 'object'>, 'TabError': <type 'exceptions.TabError'>, 'callable': <built-in function callable>, 'ZeroDivisionError': <type 'exceptions.ZeroDivisionError'>, 'eval': <built-in function eval>, '__debug__': True, 'IndentationError': <type 'exceptions.IndentationError'>, 'AssertionError': <type 'exceptions.AssertionError'>, 'classmethod': <type 'classmethod'>, 'UnboundLocalError': <type 'exceptions.UnboundLocalError'>, 'NotImplementedError': <type 'exceptions.NotImplementedError'>, 'AttributeError': <type 'exceptions.AttributeError'>, 'OverflowError': <type 'exceptions.OverflowError'>}
['__class__', '__cmp__', '__contains__', '__delattr__', '__delitem__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'clear', 'copy', 'fromkeys', 'get', 'has_key', 'items', 'iteritems', 'iterkeys', 'itervalues', 'keys', 'pop', 'popitem', 'setdefault', 'update', 'values', 'viewitems', 'viewkeys', 'viewvalues']
UPDATE to the concern that all or isinstance has been redefined.
when I tab `all()` I get:
all(a, axis=None, out=None, keepdims=False)
Test whether all array elements along a given axis evaluate to True.
It is weird that it prints 'asdf' in the second example in the screenshot
UPDATE to concern that each item in list is a list, even though it appears to
be a strong: It's a bit difficult to reproduce the code for wikiinfo_df
because it includes getting data off freebase.
for i in test:
print type(i)
<type 'str'>
<type 'str'>
<type 'str'>
<type 'str'>
<type 'str'>
<type 'str'>
<type 'str'>
Answer: In python 2.7 (assumed because of `print lst`) you should have result of
[`help(all)`](https://docs.python.org/2/library/functions.html#all) like this:
all(iterable) -> bool
Return True if bool(x) is True for all values x in the iterable.
If the iterable is empty, return True.
So you probably load some module or code that replaces it, try using:
if __builtins__.all(isinstance(i, list) for i in lst):
...
|
pyjamas - pyjsbuild error due to DistributionNotFound
Question: I am trying to build the HelloWorld example page from the Pyjamas example
folder. However I am receiving this error when I run: `sudo pyjsbuild
helloworld.py`. This error seems pretty universal to python as it seems to be
related to the setup/configuration of my python environment. Any advice on
where to look for the problem?
Here is the error
Traceback (most recent call last):
File "/usr/local/bin/pyjsbuild", line 5, in <module>
from pkg_resources import load_entry_point
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources.py", line 2603, in <module>
working_set.require(__requires__)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources.py", line 666, in require
needed = self.resolve(parse_requirements(requirements))
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources.py", line 565, in resolve
raise DistributionNotFound(req) # XXX put more info here
pkg_resources.DistributionNotFound: six
Answer: After trying the various answers, it turns out `pip` was not properly
installing the `six` package, whatever that is. So I ran `sudo easy_install
pip (--upgrade)` to make sure the script configuration was right. It wrote
some extra files so I assume that's why my next command `sudo pip install six`
or `sudo pip install six --upgrade` worked. Now I ran into another error -_-,
For anyone looking later: `Runtime Error: Top module not found 'hello world'`
Edit: The top module error is coming from trying to build into the output
folder that is not `pyjs/`. All I had to do was move the folder up to `pyjs/`
folder in `sitepackages/`.
|
Python display specific values on x-axis using matplotlib
Question: I'm querying data from a simple sqlite3 DB which is pulling a list of the
number of connections per port observed on my system. I'm trying to graph this
into a simple bar-chart using matplotlib.
Thus far, I'm using the follow code:
import matplotlib as mpl
mpl.use('Agg') # force no x11
import matplotlib.pyplot as plt
import sqlite3
con = sqlite3.connect('test.db')
cur = con.cursor()
cur.execute('''
SELECT dst_port, count(dst_port) as count from logs
where dst_port != 0
group by dst_port
order by count desc;
'''
)
data = cur.fetchall()
dst_ports, dst_port_count = zip(*data)
#dst_ports = [22, 53223, 40959, 80, 3389, 23, 443, 35829, 8080, 4899, 21320, 445, 3128, 44783, 4491, 9981, 8001, 21, 1080, 8081, 3306, 8002, 8090]
#dst_port_count = [5005, 145, 117, 41, 34, 21, 17, 16, 15, 11, 11, 8, 8, 8, 6, 6, 4, 3, 3, 3, 1, 1, 1]
print dst_ports
print dst_port_count
fig = plt.figure()
# aesthetics and data
plt.grid()
plt.bar(dst_ports, dst_port_count, align='center')
#plt.xticks(dst_ports)
# labels
plt.title('Number of connections to port')
plt.xlabel('Destination Port')
plt.ylabel('Connection Attempts')
# save figure
fig.savefig('temp.png')
When I run the above, the data is successful retrieved from the DB and a graph
is generated. However, the graph isn't what I was expecting. For example, on
the x-axis, it plots all values between 0 and 5005. I'm looking for it to
display only the values in dst_ports. I've tried using xticks but this doesn't
work either.
I've included some sample data in the above code which I've commented out that
may be useful.
In addition, here is an example of the graph output from the above code:
And also a grpah when using xticks:
Answer: You need to create some xdata by `np.arange()`:
import matplotlib as mpl
import numpy as np
import matplotlib.pyplot as plt
dst_ports = [22, 53223, 40959, 80, 3389, 23, 443, 35829, 8080, 4899, 21320, 445, 3128, 44783, 4491, 9981, 8001, 21, 1080, 8081, 3306, 8002, 8090]
dst_port_count = [5005, 145, 117, 41, 34, 21, 17, 16, 15, 11, 11, 8, 8, 8, 6, 6, 4, 3, 3, 3, 1, 1, 1]
fig = plt.figure(figsize=(12, 4))
# aesthetics and data
plt.grid()
x = np.arange(1, len(dst_ports)+1)
plt.bar(x, dst_port_count, align='center')
plt.xticks(x, dst_ports, rotation=45)
# labels
plt.title('Number of connections to port')
plt.xlabel('Destination Port')
plt.ylabel('Connection Attempts')
Here is the output:
|
Curve fitting to a Planck's Curve
Question: So I am aiming to fit my own data points to a blackbody curve, however am
having difficulties.
The outline of what I am doing is on
<http://python4esac.github.io/fitting/example_blackbody.html>
But they use random data, I am trying to use my own CSV data.
This data is:
Wavelength
0.7,
0.865,
1.24,
1.61,
3.7,
4.05,
Radiance
0,
0.106718,
0.227031,
0.373527,
0.240927,
0.293215,
Is there anyway to get Python to go into the file and use these two columns
instead? Everything I have tried so far has failed.
my code is as follows
import csv
with open('PythonCode1.csv', 'rb') as f:
reader = csv.reader(f, delimiter=',')
for row in reader:
from scipy.optimize import curve_fit
import pylab as plt
from pylab import plotfile, show, gca
fid=open('PythonCode1.csv','r')
import numpy as np
import matplotlib.cbook as cbook
def blackbody_lam(lam, T):
""" Blackbody as a function of wavelength (um) and temperature (K).
"""
from scipy.constants import h,k,c
lam = 1e-6 * lam # convert to metres
return 2*h*c**2 / (lam**5 * (np.exp(h*c / (lam*k*T)) - 1))
wa = np.linspace(0.1, 6, 100) # wavelengths in um
T1 = 1000.
T2 = 2500.
y1 = blackbody_lam(wa, T1)
y2 = blackbody_lam(wa, T2)
ytot = y1 + y2
sigma = np.ones(len(wa)) * 1 * np.median(ytot)
ydata = ytot + csv.row[1].randn(len(wa)) * sigma
and returns
%run "d:\temp\k1339544\tmpskczzu.py"
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
R:\Canpy103.001\Canopy32\App\appdata\canopy-1.0.3.1262.win-x86\lib\site- packages\IPython\utils\py3compat.pyc in execfile(fname, glob, loc)
174 else:
175 filename = fname
--> 176 exec compile(scripttext, filename, 'exec') in glob, loc
177 else:
178 def execfile(fname, *where):
d:\temp\k1339544\tmpskczzu.py in <module>()
27
28 sigma = np.ones(len(wa)) * 1 * np.median(ytot)
---> 29 ydata = ytot + csv.rows[1].randn(len(wa)) * sigma
30
31 # plot the input model and synthetic data
AttributeError: 'module' object has no attribute 'rows'
Answer: Instead of setting `wa` and `ydata` to artificial data, as was done in the
example, you want to provide your own data.
If you format your data as two columns:
Wavelength,Radiance
0.7,0
0.865,0.106718
1.24,0.227031
1.61,0.373527
3.7,0.240927
4.05,0.293215
then you can ingest it with
data = np.loadtxt("PythonCode1.csv", delimiter=",", skiprows=1)
wa = data[:,0]
ydata = data[:,1]
This won't guarantee that the function can fit your data (it can't, the
blackbody function lacks an adjustable scale parameter) or that the fit will
converge, but this is the simplest way to get the data in.
|
Python looping through string and matching it with with wildcard pattern
Question:
string1="abc"
string2="abdabcdfg"
I want to find if string1 is substring of string2. However, there are wildcard
characters like `"."` can be any letter, `y` can be `"a"` or `"d"`, `x` can be
`"b"` or `"c"`. as a result, `".yx"` will be substring of `string2`.
How can I code it using only one loop? I want to loop through string2 and make
comparisons at each index. i tried dictionary but I wand to use loop my code:
def wildcard(string,substring):
sum=""
table={'A': '.', 'C': '.', 'G': '.', 'T': '.','A': 'x', 'T': 'x', 'C': 'y', 'G': 'y'}
for c in strand:
if (c in table) and table[c] not in sum:
sum+=table[c]
elif c not in table:
sum+=c
if sum==substring:
return True
else:
return False
print wildcard("TTAGTTA","xyT.")#should be true
Answer: I know you are specifically asking for a solution using a loop. However, I
would suppose a different approach: You can easily translate your pattern to a
[regular expression](https://docs.python.org/2/howto/regex.html). This is a
similar language for string patterns, just much more powerful. You can then
use the `re` module to check whether that regular expression (and thus your
substring pattern) can be found in the string.
def to_regex(pattern, table):
# join substitutions from table, using c itself as default
return ''.join(table.get(c, c) for c in pattern)
import re
symbols = {'.': '[a-z]', '#': '[ad]', '+': '[bc]'}
print re.findall(to_regex('.+#', symbols), 'abdabcdfg')
If you prefer a more "hands-on" solution, you can use this, using loops.
def find_matches(pattern, table, string):
for i in range(len(string) - len(pattern) + 1):
# for each possible starting position, check the pattern
for j, c in enumerate(pattern):
if string[i+j] not in table.get(c, c):
break # character does not match
else:
# loop completed without triggering the break
yield string[i : i + len(pattern)]
symbols = {'.': 'abcdefghijklmnopqrstuvwxyz', '#': 'ad', '+': 'bc'}
print list(find_matches('.+#', symbols, 'abdabcdfg'))
Output in both cases is `['abd', 'bcd']`, i.e. it can be found two times,
using these substitutions.
|
i got invalid request response from google maps api in python when I copy the link to chrome it works fine
Question: What can be the reson?
{
"html_attributions" : [],
"results" : [],
"status" : "INVALID_REQUEST"
}
in Chrome fine:
{
"html_attributions": [],
"next_page_token": "CqQDkgEAAFOOGlx1ov_HPteOZTqmNHkYFmUDfDDmlQn0XpcBzeYWgCNmexMAOS1KRvaStWwFRvLDDKEUsGyFwguXrBHTuvdfmu4REV4VPH-ALqsxb7cl9wrRLhUQTyjnMilf68qgafL2Eb7GZ3OXH2s4vpsC2HRaclVPbp53kz1NZY7NeKDNPzUOW-tIHpw_X3U_2NhfUbDu-1gMFOOaMCOoaQt7FHW51ktIm4UFrn6OfytS_VdIp7RgOMp1HISIbx8GW2l1MKnUZaPEztlwJi3OvK9n4waWOvS7uUd_PPy1xPYJWv-yKtG3Ehok-LOjCv-jkB_Ki4uqjWCGW4kD5L_aKp2gjECT-ny-1aTpjtJc8a9p1Fhx_Wdbf2vee5hCZfbaSxseRgsHd0POFPaIFwIZYg6GJHHkbjW6gfbnI67oI9nC3dTH86gWzyFCsG_n0hyhCg-oHzO3mxlaDDxCM6xv1Nbp5AY4u03NGIpzTNoRekJ-EtA1d7cYu-yZ2XFzHXJGkxyWHobe_UdwLa6b4ZUQD8qCoKGQ429MxeY6x5R05AYg4Q1BEhA7UkpwystS_CoYKCCJXeoZGhRToQEqwA-RwiEMbAqwfN3n89aVZg",
"results": [...],
"status": "OK"
}
The code:
# -*- coding: utf-8 -*-
import urllib
import json
import csv
import hashlib
import time
YOUR_API_KEY = "SECRET"
def geocode(addr):
url = ("http://maps.googleapis.com/maps/api/"
"geocode/json?address=%s&sensor=false") % (urllib.quote(addr))
data = urllib.urlopen(url).read()
info = json.loads(data).get("results")[0].get("geometry").get("location")
return info
def geocode2(r):
info = []
url_base = ("https://maps.googleapis.com/maps/api/place/search/json?"
"location=%s,%s&radius=500&types=food&sensor=false&"
"key=%s&pagetoken=%s") % (
r['lat'],
r['lng'],
YOUR_API_KEY,
''
)
data = urllib.urlopen(url_base).read()
info.extend(json.loads(data).get("results"))
token = json.loads(data).get("next_page_token")
while token:
time.sleep(5)
new_url = url_base + token
data = urllib.urlopen(new_url).read()
token = json.loads(data).get("next_page_token")
info.extend(json.loads(data).get("results"))
print len(info)
l = []
for i in info:
t = (i["name"],
i["vicinity"],
i["geometry"]["location"]["lat"],
i["geometry"]["location"]["lng"]
)
l.append(t)
return l
for place in geocode2(geocode('Polska, Warszawa, Pl. Zawiszy 1')):
print place
The output: <https://gist.github.com/andilab/078ea76b1f4d70704b50>
Answer: I guess it is much about time. I added time.sleep(5) in while loop where I try
fetching new google places with next_page_token() and it works.
The quota from docs confirms my guess.
> The maximum number of results that can be returned is 60. **There is a short
> delay between when a next_page_token is issued, and when it will become
> valid.**
From: [Google Places API
Doc](https://developers.google.com/places/documentation/search)
Worth mention, that anyway maximum number of places returned will be **60**!
|
Create square thumbnails with Python + MagickWand
Question: How can I create square thumbnails with Python and Wand? I'm trying to make
square thumbnails from source images of any size. It's important that the
thumbnail have the same aspect ratio as the original, cropping is ok, and it
should fill the sapce of the thumbnail.
Answer: The following `crop_center()` function makes the given image square.
from __future__ import division
from wand.image import Image
def crop_center(image):
dst_landscape = 1 > image.width / image.height
wh = image.width if dst_landscape else image.height
image.crop(
left=int((image.width - wh) / 2),
top=int((image.height - wh) / 2),
width=int(wh),
height=int(wh)
)
First you need to make the image square, and then you can
[`resize()`](http://docs.wand-
py.org/en/0.3.7/wand/image.html#wand.image.BaseImage.resize) the square
smaller.
|
How to destroy a parent window when child window's red X is clicked in Tkinter 8.5 and Python 3.3
Question: Newbie question here. I would like for `secondWindow` to be destroyed in
addition to `thirdWindow` when the red X is clicked in `thirdWindow`, just
like what happens when you click `thirdButton` in `thirdWindow`. `firstWindow`
should remain alive.
Below is some example code:
import tkinter
from tkinter import ttk
def secondWindow():
secondWindow = tkinter.Toplevel(firstWindow)
secondFrame = ttk.Frame(secondWindow)
secondFrame.pack()
secondButton = ttk.Button(secondFrame, text="proceed to 3rd window",\
command=lambda: thirdWindow(secondWindow))
secondButton.pack()
def thirdWindow(parent):
thirdWindow = tkinter.Toplevel(parent)
thirdFrame = ttk.Frame(thirdWindow)
thirdFrame.pack()
thirdButton = ttk.Button(thirdFrame, text="close 2nd and 3rd windows",\
command=lambda: destroy(thirdWindow, parent))
thirdButton.pack()
def destroy(self, parent):
self.destroy()
parent.destroy()
firstWindow = tkinter.Tk()
firstFrame = ttk.Frame(firstWindow)
firstFrame.pack()
firstButton = ttk.Button(firstFrame, text="proceed to 2nd window",\
command=secondWindow)
firstButton.pack()
firstWindow.mainloop()
Thanks in advance for any help you can provide!
Answer: Use `parent` to run `parent` function or get variable from `parent` \- for
example to get its `parent` or run function which close its parent.
import tkinter
from tkinter import ttk
def secondWindow(parent):
secondWindow = tkinter.Toplevel(parent)
secondWindow.parent = parent # remember parent
secondFrame = ttk.Frame(secondWindow)
secondFrame.pack()
secondButton = ttk.Button(secondFrame, text="proceed to 3rd window",\
command=lambda: thirdWindow(secondWindow))
secondButton.pack()
def thirdWindow(parent):
thirdWindow = tkinter.Toplevel(parent)
thirdWindow.parent = parent # remember parent
thirdFrame = ttk.Frame(thirdWindow)
thirdFrame.pack()
thirdButton = ttk.Button(thirdFrame, text="close 2nd and 3rd windows",\
command=lambda: destroy(thirdWindow))
thirdButton.pack()
def destroy(self):
self.parent.parent.destroy() # destroy grand-parent and all children are dead too.
firstWindow = tkinter.Tk()
firstFrame = ttk.Frame(firstWindow)
firstFrame.pack()
firstButton = ttk.Button(firstFrame, text="proceed to 2nd window",\
command=lambda:secondWindow(firstWindow))
firstButton.pack()
firstWindow.mainloop()
|
Issue "removing" a block of lines from a .sql file
Question: I'm working on a script that will remove a block of lines from a SQL dump
(basically, cleanse any table we do not want to restore). I thought I had it
working, but when trying to restore the resulting file to my database I
realized that when the script rewrites to the file, it's missing more lines
than it should, and the restore fails. Here's my paltry attempt at this:
#!/usr/bin/python
to_keep = []
to_remove = []
f = open("backuptest.sql","r")
lines = f.readlines()
f.close()
### Function to remove lines associated with a table block
def remove_lines(table_name):
for i in range(0, len(lines)):
line = lines[i]
if "structure" in line and table_name in line:
for j in range(i, len(lines)):
to_remove.append(lines[j])
if "UNLOCK TABLES;" in lines[j]:
break
if line not in to_remove:
to_keep.append(line)
f.write(line)
print "Finding lines"
f = open("backuptest.sql", "w")
remove_lines("advanced_searches")
f.close()
f = open("backuptest.sql", "w")
remove_lines("test_table2")
f.close()
f = open("backuptest.sql", "w")
remove_lines("test_table3")
f.close()
And here's what one of the blocks of the sql file looks like, for reference:
-- Table structure for table `advanced_searches`
--
DROP TABLE IF EXISTS `advanced_searches`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `advanced_searches` (
`batch_size` int(11) NOT NULL DEFAULT '0'
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
/*!40101 SET character_set_client = @saved_cs_client */;
--
-- Dumping data for table `advanced_searches`
--
LOCK TABLES `advanced_searches` WRITE;
/*!40000 ALTER TABLE `advanced_searches` DISABLE KEYS */;
/*!40000 ALTER TABLE `advanced_searches` ENABLE KEYS */;
UNLOCK TABLES;
I start the script by matching against the first line in such a block
(includes the word "structure" and the table name), then I'm attempting to
iterate from that line through "UNLOCK TABLES;" What's happening instead is
it's removing ALL instances of "UNLOCK TABLES;" in the script, even from
blocks I do not want removed, and it's also removing the following line from
each block as well " ) ENGINE=MyISAM DEFAULT CHARSET=utf8
COLLATE=utf8_unicode_ci; " (The closing parentheses through the rest of that
line).
Thanks for any help. I'll keep plugging away at what I've missed.
Answer: # Try `sqlparse`
$ pip install sqlparse
Quick test from tutorial:
>>> import sqlparse
>>> sql = "select * from foo; select * from bar;"
>>> res = sqlparse.split(sql)
>>> res
[u'select * from foo;', u'select * from bar;']
Applying to your SQL script:
>>> sql = """-- Table structure for table `advanced_searches`
... --
...
... DROP TABLE IF EXISTS `advanced_searches`;
... /*!40101 SET @saved_cs_client = @@character_set_client */;
... /*!40101 SET character_set_client = utf8 */;
... CREATE TABLE `advanced_searches` (
... `batch_size` int(11) NOT NULL DEFAULT '0'
... ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
... /*!40101 SET character_set_client = @saved_cs_client */;
...
... --
... -- Dumping data for table `advanced_searches`
... --
...
... LOCK TABLES `advanced_searches` WRITE;
... /*!40000 ALTER TABLE `advanced_searches` DISABLE KEYS */;
... /*!40000 ALTER TABLE `advanced_searches` ENABLE KEYS */;
... UNLOCK TABLES;"""
...
>>> res = sqlparse.split(sql)
>>> res
[u'-- Table structure for table `advanced_searches`\n--\n\nDROP TABLE IF EXISTS `advanced_searches`;',
u'/*!40101 SET @saved_cs_client = @@character_set_client */;',
u'/*!40101 SET character_set_client = utf8 */;',
u"CREATE TABLE `advanced_searches` (\n `batch_size` int(11) NOT NULL DEFAULT '0'\n) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;",
u'/*!40101 SET character_set_client = @saved_cs_client */;',
u'--\n-- Dumping data for table `advanced_searches`\n--\n\nLOCK TABLES `advanced_searches` WRITE;',
u'/*!40000 ALTER TABLE `advanced_searches` DISABLE KEYS */;',
u'/*!40000 ALTER TABLE `advanced_searches` ENABLE KEYS */;',
u'UNLOCK TABLES;']
This provides properly parsed script and last thing to do, is to filter it one
by one, picking only those, which seem to be needed. This I leave to you.
|
How to do a loop inside of a loop in python
Question: Currently I have a program which goes through a list of vector coordinates and
performs a simple math function on the two vectors, but I want to make a loop
inside of a loop to be able to have more control on what happens, this is my
program so far:
import operator
import numpy as np
b = 0
a = 1
for a in range(0,56):
vector1 = (int(l[b][0]),int(l[b][1]),int(l[b][2]))
vector2 = (int(l[a][0]),int(l[a][1]),int(l[a][2]))
#print vector1
#print vector2
x = vector1
y = vector2
vector3 = list(np.array(x) - np.array(y))
#print vector3
dotProduct = reduce( operator.add, map( operator.mul, vector3, vector3))
print dotProduct
a += 1
But what I want is that once a hits 56 and does its final run through, I want
B to add 1 and a to reset back to zero, and redo the loop of operations until
b goes up to 55.
Desired output: example of coordiantes:
Cu 46.7176 27.1121 27.1121
Cu 43.2505 36.0618 32.4879
Cu 43.3392 36.0964 28.9236
Cu 43.2509 37.8362 27.1091
Cu 34.4872 14.1794 16.5767
Cu 34.4103 16.0364 14.3521
Cu 32.7006 14.069 14.412
and I want the first coordinate to perform the dot product with everything
under it, and go back and then start with the second coordinate and perform
dot product with everything under it, and so on..
Answer: You can do a nested for loop. Below is what you want:
for b in range(0, 56):
for a in range(0, 57):
|
How to convert 4 byte IEEE (little endian) float binary representation to float
Question: I am decoding a binary file, which has decimal numbers represented by four
bytes, little endian. For example, `94 53 F0 40` represents 7.510202.
Unfortunately, Python is giving me 7.51020240784.
When I try to parse this data using `unpack("<f",sampledata)[0]` I don't get
exact representations of the original, due to the way Python stores values
(for more information, see <http://bugs.python.org/issue4114>).
Unfortunately, I _do_ need to get the _exact_ same representation- regardless
of discussions about the inaccuray of floats, because I need to write these
values to a text file, with the same number of decimal places as they were
initially written to the binary file with.
I'd rather stick to Python if possible, but am happy to implement a solution
in C if necessary. The reason I cannot simply truncate the return of the
unpack function, is that I cannot guarantee how many decimal places the
original float had, for example `0C 02 0F 41` represents 8.938 according to my
hex editor, from the original binary file, which only has 3 decimal places.
To be clear, I need to take four hex bytes as my input, and output either a
text/ASCII or number representation of the IEEE 32-bit floating point number,
that has the same number of decimal places as was intended by the creator of
the file. The output I will use to create a CSV of the original binary data
file, not for actually performing any calculations.
Any suggestions?
Example:
from __future__ import print_function
from struct import *
print("Should print 7.510202")
hexbytes = b"\x94\x53\xF0\x40"
# 01101001 11001000 11110001 01000000
# should print 7.510202
print(unpack("<f",hexbytes)[0])
Answer: A 4-byte IEEE format floating point number holds approximately 7 digits. What
you want to do is round the result of `unpack` to a total of 7 digits. From
there the normal Python conversion from float to string will hide all the
floating point nastiness from you.
def magnitude(x):
return 0 if x==0 else int(math.floor(math.log10(abs(x)))) + 1
def round_total_digits(x, digits=7):
return round(x, digits - magnitude(x))
>>> round_total_digits(struct.unpack('<f', '\x94\x53\xF0\x40')[0])
7.510202
>>> round_total_digits(struct.unpack('<f', '\x0C\x02\x0F\x41')[0])
8.938
>>> x = struct.unpack('<f', struct.pack('<f', 12345.67))[0]
>>> x
12345.669921875
>>> round_total_digits(x)
12345.67
Note that if your numbers did not originate from a direct conversion of a
decimal number but were the result of a calculation, this could _reduce_ the
total accuracy. But not by much.
|
Syntax Error using import ctypes
Question: I'm new to python and have installed Python2.6 directory address of python is
"C:\Python26"
I tried to use import ctypes
I'm getting below errors
Traceback (most recent call last):
File "C:\Python26\Lib\msdecmiolib\__init__.py", line 22, in <module>
import ctypes
File "C:\Python26\Lib\ctypes\__init__.py", line 25
5DEFAULT_MODE = RTLD_LOCAL
^
SyntaxError: invalid syntax.
Answer: Something's wrong with your Python installation; that line in
`ctypes/__init__.py` should simply read
DEFAULT_MODE = RTLD_LOCAL
It's hard to imagine how that could have happened other than accidentally --
maybe you opened the file to look at it and accidentally hit `5` before
saving? Anyway, you can either fix it yourself and see what happens or if
you'd prefer reinstall Python.
(Possibly upgrading to at least 2.7 while you're at it, which would be a good
idea unless there's some peculiar reason you can't, although that's up to
you.)
|
Much more Efficient way to Parse and Process Large files with Json Objects
Question: This is by far the craziest question I have asked on SO but I am going to give
it a shot in the hope of getting some advice about whether or not I am
leveraging the right tools and methods for processing large amounts of data
efficiently. I'm not necessarily looking for help on optimizing my code unless
there is something I am completely overlooking but essentially would just like
to know if I should be going with a different framework all together instead
of Python. I'm new enough to Python to not be completely sure if it is
possible to process large amount of data and store into DB much more
efficiently. Essentially the below implementation reads text files in a
directory with each text file containing 50K lines of json objects that need
to be parsed and read and then converted into a csv before loading into a
database. I hate using list containers and I am hoping that there is something
else I can research implementing in Python for doing this in a much much
better way. My initial thoughts are that I should be researching using
generators but not totally sure. The crazy concat part at the end is important
because it converts a comma separated list into it's own rows. [Converting
Column with string separated values into
rows](http://stackoverflow.com/questions/24419551/converting-column-with-
string-separated-values-into-rows)
triggerZipFiles = glob.glob('*.zip')
for triggerFiles in triggerZipFiles:
with zipfile.ZipFile(triggerFiles, 'r') as myzip:
for logfile in myzip.namelist():
datacc = []
zipcc = []
csvout = '{}_US.csv'.format(logfile[:-4])
f = myzip.open(logfile)
contents = f.readlines()
for line in contents:
try:
parsed = json.loads(line[:-2])
if "CC" in parsed['data']['weatherType'] and "US" in parsed['zipcodes']:
datacc.append(parsed['data'])
zipcc.append(parsed['zipcodes'])
except:
pass
if len(datacc) > 0:
df = pd.concat([pd.DataFrame(zipcc), pd.DataFrame(datacc)], axis=1)
df = pd.concat((pd.Series((v, row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key'], row['key'], row['key'],
row['key'], row['key'], row['key'], row['key']), df.columns) for _,
row in df.iterrows() for v in row['US']), axis=1).T
df.to_csv(csvout, header=None, index=False)
else:
pass
print datetime.now().strftime('%Y/%m/%d %H:%M:%S') + ": Finished: {}".format(logfile)
Answer: Firstly, _lines_ isn't a particularly useful metric when it comes to json!
Secondly, you've got the right idea: you definitely want to do this chunk-
based (read/clean/dump each part separately).
I recommend using pandas' `read_json` function, it's much more efficient at
creating DataFrames (it doesn't create a temporary python dict), _see
the[reading in json section of the docs](http://pandas.pydata.org/pandas-
docs/dev/io.html#reading-json)._
* If there not _actually_ json, then doing string manipulation to make them json is usually your best bet.*
* If you have "oddly-shaped" json, then you can either [`json_normalize`](http://pandas.pydata.org/pandas-docs/dev/io.html#normalization) when reading, or parse the columns which contain multiple columns after reading in the DataFrame (e.g. using a Series string method or apply).
_*it's unclear what the actual format is, but often it doesn't take much to
make them into**valid** json._
Python bonus tip: if you're more that a few indentation levels deep consider
breaking it apart into more functions. (The obvious choice here is to have
`f1(logfile)` and `f2(line)`, but using descriptive names...)
|
looking for example for QCompleter with segmented completion / tree models
Question: The PySide docs include this section on [QCompleter with tree
models](http://srinikom.github.io/pyside-
docs/PySide/QtGui/QCompleter.html#pyside-qtgui-qcompleter-handling-tree-
models):
> PySide.QtGui.QCompleter can look for completions in tree models, assuming
> that any item (or sub-item or sub-sub-item) can be unambiguously represented
> as a string by specifying the path to the item. The completion is then
> performed one level at a time.
>
> Let’s take the example of a user typing in a file system path. The model is
> a (hierarchical) PySide.QtGui.QFileSystemModel . The completion occurs for
> every element in the path. For example, if the current text is C:\Wind ,
> PySide.QtGui.QCompleter might suggest Windows to complete the current path
> element. Similarly, if the current text is C:\Windows\Sy ,
> PySide.QtGui.QCompleter might suggest System .
>
> For this kind of completion to work, PySide.QtGui.QCompleter needs to be
> able to split the path into a list of strings that are matched at each
> level. For C:\Windows\Sy , it needs to be split as “C:”, “Windows” and “Sy”.
> The default implementation of PySide.QtGui.QCompleter.splitPath() , splits
> the PySide.QtGui.QCompleter.completionPrefix() using QDir.separator() if the
> model is a PySide.QtGui.QFileSystemModel .
>
> To provide completions, PySide.QtGui.QCompleter needs to know the path from
> an index. This is provided by PySide.QtGui.QCompleter.pathFromIndex() . The
> default implementation of PySide.QtGui.QCompleter.pathFromIndex() , returns
> the data for the edit role for list models and the absolute file path if the
> mode is a PySide.QtGui.QFileSystemModel.
But I can't seem to find an example showing how to do this. **Can anyone point
me at an example I can use as a starting point?** (In my investigation it
looks like maybe the hard part is the tree model rather than the QCompleter)
It looks like you would need to provide these functions:
* ability to split a string into segments (for the example given, `C:\Windows\Sy` to `['C:','Windows','Sy']`
* the ability to specify the list of items that include the last segment (e.g. all the items included in `['C:','Windows']`
I found an example for the basic functionality of QCompleter and have been
able to tweak the basics fine (see below), I just don't know how to go about
implementing a tree model type application.
'''based on
http://codeprogress.com/python/libraries/pyqt/showPyQTExample.php?index=403&key=QCompleterQLineEdit'''
from PySide.QtGui import *
from PySide.QtCore import *
import sys
def main():
app = QApplication(sys.argv)
edit = QLineEdit()
strList = '''
Germany;Russia;France;
french fries;frizzy hair;fennel;fuzzball
frayed;fickle;Frobozz;fear;framing;frames
Franco-American;Frames;fancy;fire;frozen yogurt
football;fnord;foul;fowl;foo;bar;baz;quux
family;Fozzie Bear;flinch;fizzy;famous;fellow
friend;fog;foil;far;flower;flour;Florida
'''.replace('\n',';').split(";")
strList.sort(key=lambda s: s.lower())
completer = QCompleter(strList,edit)
completer.setCaseSensitivity(Qt.CaseInsensitive)
edit.setWindowTitle("PySide QLineEdit Auto Complete")
edit.setCompleter(completer)
edit.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
Answer: I couldn't find a good example for what I wanted, but I figured out how to
adapt the Qt TreeModel example to using a QCompleter:
<https://gist.github.com/jason-s/9dcef741288b6509d362>
The QCompleter is the easy part, you just have to tell it how to split a path
into segments, and then how to get from a particular entry in the model back
to a path:
class MyCompleter(QtGui.QCompleter):
def splitPath(self, path):
return path.split('/')
def pathFromIndex(self, index):
result = []
while index.isValid():
result = [self.model().data(index, QtCore.Qt.DisplayRole)] + result
index = index.parent()
r = '/'.join(result)
return r
Aside from that, you have to configure the QCompleter properly, telling it how
to get from a model item to a text string. Here I set it up to use the
DisplayRole and to use column 0.
edit = QtGui.QLineEdit()
completer = MyCompleter(edit)
completer.setModel(model)
completer.setCompletionColumn(0)
completer.setCompletionRole(QtCore.Qt.DisplayRole)
completer.setCaseSensitivity(QtCore.Qt.CaseInsensitive)
|
Numpy PIL Python : crop image on whitespace or crop text with histogram Thresholds
Question: How would I go about finding the bounding box or window for the region of
whitespace surrounding the numbers in the image below?:
# Original image:
Height: 762 pixels Width: 1014 pixels
# Goal:
Something like: `{x-bound:[x-upper,x-lower], y-bound:[y-upper,y-lower]}` so I
can crop to the text and input into tesseract or some OCR.
# Attempts:
I had thought of slicing the image into hard coded chunk sizes and analysing
at random, but i think it would be too slow.
Example code using `pyplot` adapted from ([Using python and PIL how can I grab
a block of text in an
image?](http://stackoverflow.com/questions/9402765/using-python-and-pil-how-
can-i-grab-a-block-of-text-in-an-image)):
from PIL import Image
import numpy as np
import matplotlib.pyplot as plt
im = Image.open('/home/jmunsch/Pictures/Aet62.png')
p = np.array(im)
p = p[:,:,0:3]
p = 255 - p
lx,ly,lz = p.shape
plt.plot(p.sum(axis=1))
plt.plot(p.sum(axis=0))
#I was thinking something like this
#The image is a 3-dimensional ndarray [[x],[y],[color?]]
#Set each value below an axes mean to 0
[item = 0 for item in p[axis=0] if item < p.mean(axis=0)]
# and then some type of enumerated groupby for each axes
#finding the mean index for each groupby(0) on axes
plt.plot(p[mean_index1:mean_index2,mean_index3:mean_index4])
Based on the graphs each of the valleys would indicate a place to bound.
* The first graph shows where lines of text would be
* The second graph shows where characters would be
# Plot example `plt.plot(p.sum(axis=1))`:
# Plot example output `plt.plot(p.sum(axis=0))`:
Related posts/docs:
* [Trim whitespace using PIL](http://stackoverflow.com/questions/10615901/trim-whitespace-using-pil)
* [Using python and PIL how can I grab a block of text in an image?](http://stackoverflow.com/questions/9402765/using-python-and-pil-how-can-i-grab-a-block-of-text-in-an-image)
* [Use Python / PIL or similar to shrink whitespace](http://stackoverflow.com/questions/9396312/use-python-pil-or-similar-to-shrink-whitespace/9398422#9398422)
* [Crop the image using PIL in python](http://stackoverflow.com/questions/9983263/crop-the-image-using-pil-in-python)
* [Rectangular bounding box around blobs in a monochrome image using python](http://stackoverflow.com/questions/9525313/rectangular-bounding-box-around-blobs-in-a-monochrome-image-using-python?rq=1)
* [How can I improve my paw detection?](http://stackoverflow.com/questions/4087919/how-can-i-improve-my-paw-detection?lq=1)
* <http://scipy-lectures.github.io/advanced/image_processing/>
* <http://docs.scipy.org/doc/numpy/reference/generated/numpy.ndarray.html>
# update: solution by HYRY
Answer: I think you can use Morphology functions in `scipy.ndimage`, here is an
example:
import pylab as pl
import numpy as np
from scipy import ndimage
img = pl.imread("Aet62.png")[:, :, 0].astype(np.uint8)
img2 = ndimage.binary_erosion(img, iterations=40)
img3 = ndimage.binary_dilation(img2, iterations=40)
labels, n = ndimage.label(img3)
counts = np.bincount(labels.ravel())
counts[0] = 0
img4 = labels==np.argmax(counts)
img5 = ndimage.binary_fill_holes(img4)
result = ~img & img5
result = ndimage.binary_erosion(result, iterations=3)
result = ndimage.binary_dilation(result, iterations=3)
pl.imshow(result, cmap="gray")
the output is:
|
Get new result in infinite loop with SqlAlchemy
Question: I'm new to Python - coming from PHP - and have been bouncing back and forth
between Python official documentation and SqlAlchemy (which I'm trying to use
as easily as Laravel's DB class)
I have this bit of code:
from sqlalchemy import *
engine = create_engine('mysql://root:[email protected]/db')
db_connection = engine.connect()
meta = MetaData()
video_processing = Table('video_processing', meta, autoload=True, autoload_with=engine)
while True:
sleep(1)
stmt = select([video_processing]).where(video_processing.c.finished_processing == 0).where(video_processing.c.in_progress == 0)
result = db_connection.execute(stmt)
rows = result.fetchall()
print len(rows)
stmt = None
result = None
rows = None
When I execute my statement, I let it run and print out the number of rows
that it fetches. While that's going, I go in and delete rows from my db. The
problem is that even though I'm resetting pretty much everything I can think
of that is related to the query, it's still printing out the same number of
fetched rows in every iteration of my loop, even though I'm changing the
underlying data. Any ideas?
Answer: The tricky part is that the connection needs to be closed if using
engine.connect() with db_connection.close() otherwise you might not see new
data changes.
I ended up bypassing the connection and executing my statement directly on the
engine, which makes more sense logically anyways:
result = engine.execute(stmt)
|
NoSuchElementException when trying to use Selenium Python
Question: I keep getting a NoSuchElementException when trying to use Selenium to find an
element in python. I'm waiting for the page to fully load, and I'm switching
to the right frame (or at least I think so!).
Here is the code:
driver.get("https://www.arcgis.com/home/signin.html")
driver.implicitly_wait(10)
driver.switch_to_frame("oAuthFrame")
elem = driver.find_element_by_name('username')
elem1 = driver.find_element_by_name('password')
Here is the webpage part I'm trying to access:
<input id="user_username" class="textBox" type="text" name="username" autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false">
which is located inside
<iframe dojoattachpoint="_iFrame" id="oAuthFrame" scrolling="no" style="display: block; border: 0px;" marginheight="0" marginwidth="0" frameborder="0" width="400" height="500"...>
You can go see the source code for yourself at
<https://www.arcgis.com/home/signin.html>
Full error output:
Traceback (most recent call last):
File "C:\Python34\beginSample.py", line 12, in <module>
elem = driver.find_element_by_name('username')
File "C:\Python34\lib\site-packages\selenium\webdriver\remote\webdriver.py", l
ine 302, in find_element_by_name
return self.find_element(by=By.NAME, value=name)
File "C:\Python34\lib\site-packages\selenium\webdriver\remote\webdriver.py", l
ine 662, in find_element
{'using': by, 'value': value})['value']
File "C:\Python34\lib\site-packages\selenium\webdriver\remote\webdriver.py", l
ine 173, in execute
self.error_handler.check_response(response)
File "C:\Python34\lib\site-packages\selenium\webdriver\remote\errorhandler.py"
, line 164, in check_response
raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: 'no such element\n
(Session info: chrome=35.0.1916.153)\n (Driver info: chromedriver=2.9.248315,pl
atform=Windows NT 6.1 SP1 x86_64)'
If someone could help me figure out what's wrong, I'd greatly appreciate it.
**UPDATE** : I'm now using actions, and I've debugged to the point of no
errors, but also its not typing anything. Here is the code:
from selenium.webdriver.common.keys import Keys
from selenium.webdriver.common.action_chains import ActionChains
actions = ActionChains(driver)
actions.send_keys("sd")
actions.send_keys(Keys.TAB)
actions.send_keys("bg")
actions.perform()
Answer: Personally I try to stick with the xpath and utilize xquery functionality. You
can still use the other attachments since they are usually "attributes" of the
element, but it provides more flexibility for complex types contains
searching. I am able to find the username/password fields with the below two
attach xpaths. You shouldn't need to switch to the iframe first...although
some of the direct calls like name seem to not function...the xpath version
worked for me.
element = driver.find_element_by_xpath("//input[@name='username']")
element1 = driver.find_element_by_xpath("//input[@name='password']")
**Update** : I was able to duplicate the issue... I'm not sure why the
locators are not functioning for this specifically, but here is a work around
that works. The default placement of the focus when the page is loaded is the
username box.
actions = selenium.webdriver.common.action_chains.ActionChains(driver)
actions.SendKeys("sd").Perform()
actions.SendKeys(selenium.webdriver.common.Keys.Tab).Perform()
actions.SendKeys("bg").Perform()
<http://selenium.googlecode.com/git/docs/api/py/webdriver/selenium.webdriver.common.action_chains.html>
I'll update again if I can figure out a way to directly connect to the fields.
**Update:** With Chrome if you grab the specific iFrame you will see an error
that says your browser does not support this iFrame. I believe the
communication breakdown might be in the browser not being able to read it
correctly...even though it seems to render it and allow functionality
correctly. Since Selenium is based on the DOM selection it would be attempting
to utilize similar behaviors to find this. I would recommend trying a
`driver.execute_script("script goes here")` and trying to locate it purely
with javascript and see if that would work. You would of course then have to
continue using javascript and modify the control attributes/properties
directly with javascript and then execute a javascript submit event for the
button.
|
Async like pattern in pyqt? Or cleaner background call pattern?
Question: I'm trying to write a short(one file pyqt) program which is responsive(so
dependencies outside python/lxml/qt, especially ones I can't just stick in the
file have some downsides for this use case but I might still be willing to try
them). I'm trying to perform possibly lengthy(and cancelable) operations on a
worker thread(actually the background operation has a lock around it to
prevent multiple operations at once(since the library it uses can only be used
one call at a time) and timeouts so spawning multiple threads would be fine
also).
As far as I can figure out the "basic" way to do this with qt is. (note code
is not tested so it may be wrong)
class MainWindow(QWidget):
#self.worker moved to background thread
def initUI(self):
...
self.cmd_button.clicked.connect(self.send)
...
@pyqtslot()
def send(self):
...
...#get cmd from gui
QtCore.QTimer.singleShot(0, lambda : self.worker(cmd))
@pyqtslot(str)
def end_send(self, result):
...
...# set some gui to display result
...
class WorkerObject(QObject):
def send_cmd(self, cmd):
... get result of cmd
QtCore.QTimer.singleShot(0, lambda: self.main_window.end_send())
(Am I using QTimer right(it runs on different thread right)?)
I'd really prefer to have something simpler and more abstracted along the
lines of c#'s async. (note I haven't used asyncio so I might be getting some
things wrong)
class MainWindow(QWidget):
...
@asyncio.coroutine
def send(self):
...
...#get cmd from gui
result = yield from self.worker(cmd)
#set gui textbox to result
class WorkerObject(QObject):
@asyncio.coroutine
def send_cmd(self, cmd):
... get result of cmd
yield from loop.run_in_executor(None, self.model.send_command, cmd)
I heard that python 3 had similar features and there was a back port but does
it work properly with qt?
If anyone knows of another saner pattern. that too would be useful/an
acceptable answer.
Answer: The short answer to your question ("is there a way to use an `asyncio`-like
pattern in PyQt?") is yes, but it's pretty complicated and arguably not worth
it for a small program. Here's some prototype code that allows you to use an
asynchronous pattern like you described:
import types
import weakref
from functools import partial
from PyQt4 import QtGui
from PyQt4 import QtCore
from PyQt4.QtCore import QThread, QTimer
## The following code is borrowed from here:
# http://stackoverflow.com/questions/24689800/async-like-pattern-in-pyqt-or-cleaner-background-call-pattern
# It provides a child->parent thread-communication mechanism.
class ref(object):
"""
A weak method implementation
"""
def __init__(self, method):
try:
if method.im_self is not None:
# bound method
self._obj = weakref.ref(method.im_self)
else:
# unbound method
self._obj = None
self._func = method.im_func
self._class = method.im_class
except AttributeError:
# not a method
self._obj = None
self._func = method
self._class = None
def __call__(self):
"""
Return a new bound-method like the original, or the
original function if refers just to a function or unbound
method.
Returns None if the original object doesn't exist
"""
if self.is_dead():
return None
if self._obj is not None:
# we have an instance: return a bound method
return types.MethodType(self._func, self._obj(), self._class)
else:
# we don't have an instance: return just the function
return self._func
def is_dead(self):
"""
Returns True if the referenced callable was a bound method and
the instance no longer exists. Otherwise, return False.
"""
return self._obj is not None and self._obj() is None
def __eq__(self, other):
try:
return type(self) is type(other) and self() == other()
except:
return False
def __ne__(self, other):
return not self == other
class proxy(ref):
"""
Exactly like ref, but calling it will cause the referent method to
be called with the same arguments. If the referent's object no longer lives,
ReferenceError is raised.
If quiet is True, then a ReferenceError is not raise and the callback
silently fails if it is no longer valid.
"""
def __init__(self, method, quiet=False):
super(proxy, self).__init__(method)
self._quiet = quiet
def __call__(self, *args, **kwargs):
func = ref.__call__(self)
if func is None:
if self._quiet:
return
else:
raise ReferenceError('object is dead')
else:
return func(*args, **kwargs)
def __eq__(self, other):
try:
func1 = ref.__call__(self)
func2 = ref.__call__(other)
return type(self) == type(other) and func1 == func2
except:
return False
class CallbackEvent(QtCore.QEvent):
"""
A custom QEvent that contains a callback reference
Also provides class methods for conveniently executing
arbitrary callback, to be dispatched to the event loop.
"""
EVENT_TYPE = QtCore.QEvent.Type(QtCore.QEvent.registerEventType())
def __init__(self, func, *args, **kwargs):
super(CallbackEvent, self).__init__(self.EVENT_TYPE)
self.func = func
self.args = args
self.kwargs = kwargs
def callback(self):
"""
Convenience method to run the callable.
Equivalent to:
self.func(*self.args, **self.kwargs)
"""
self.func(*self.args, **self.kwargs)
@classmethod
def post_to(cls, receiver, func, *args, **kwargs):
"""
Post a callable to be delivered to a specific
receiver as a CallbackEvent.
It is the responsibility of this receiver to
handle the event and choose to call the callback.
"""
# We can create a weak proxy reference to the
# callback so that if the object associated with
# a bound method is deleted, it won't call a dead method
if not isinstance(func, proxy):
reference = proxy(func, quiet=True)
else:
reference = func
event = cls(reference, *args, **kwargs)
# post the event to the given receiver
QtGui.QApplication.postEvent(receiver, event)
## End borrowed code
## Begin Coroutine-framework code
class AsyncTask(QtCore.QObject):
""" Object used to manage asynchronous tasks.
This object should wrap any function that you want
to call asynchronously. It will launch the function
in a new thread, and register a listener so that
`on_finished` is called when the thread is complete.
"""
def __init__(self, func, *args, **kwargs):
super(AsyncTask, self).__init__()
self.result = None # Used for the result of the thread.
self.func = func
self.args = args
self.kwargs = kwargs
self.finished = False
self.finished_cb_ran = False
self.finished_callback = None
self.objThread = RunThreadCallback(self, self.func, self.on_finished,
*self.args, **self.kwargs)
self.objThread.start()
def customEvent(self, event):
event.callback()
def on_finished(self, result):
""" Called when the threaded operation is complete.
Saves the result of the thread, and
executes finished_callback with the result if one
exists. Also closes/cleans up the thread.
"""
self.finished = True
self.result = result
if self.finished_callback:
self.finished_ran = True
func = partial(self.finished_callback, result)
QTimer.singleShot(0, func)
self.objThread.quit()
self.objThread.wait()
class RunThreadCallback(QtCore.QThread):
""" Runs a function in a thread, and alerts the parent when done.
Uses a custom QEvent to alert the main thread of completion.
"""
def __init__(self, parent, func, on_finish, *args, **kwargs):
super(RunThreadCallback, self).__init__(parent)
self.on_finished = on_finish
self.func = func
self.args = args
self.kwargs = kwargs
def run(self):
try:
result = self.func(*self.args, **self.kwargs)
except Exception as e:
print "e is %s" % e
result = e
finally:
CallbackEvent.post_to(self.parent(), self.on_finished, result)
def coroutine(func):
""" Coroutine decorator, meant for use with AsyncTask.
This decorator must be used on any function that uses
the `yield AsyncTask(...)` pattern. It shouldn't be used
in any other case.
The decorator will yield AsyncTask objects from the
decorated generator function, and register itself to
be called when the task is complete. It will also
excplicitly call itself if the task is already
complete when it yields it.
"""
def wrapper(*args, **kwargs):
def execute(gen, input=None):
if isinstance(gen, types.GeneratorType):
if not input:
obj = next(gen)
else:
try:
obj = gen.send(input)
except StopIteration as e:
result = getattr(e, "value", None)
return result
if isinstance(obj, AsyncTask):
# Tell the thread to call `execute` when its done
# using the current generator object.
func = partial(execute, gen)
obj.finished_callback = func
if obj.finished and not obj.finished_cb_ran:
obj.on_finished(obj.result)
else:
raise Exception("Using yield is only supported with AsyncTasks.")
else:
print("result is %s" % result)
return result
result = func(*args, **kwargs)
execute(result)
return wrapper
## End coroutine-framework code
If you put the above code into a module (say `qtasync.py`) you can import it
into a script and use it like so to get `asyncio`-like behavior:
import sys
import time
from qtasync import AsyncTask, coroutine
from PyQt4 import QtGui
from PyQt4.QtCore import QThread
class MainWindow(QtGui.QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.initUI()
def initUI(self):
self.cmd_button = QtGui.QPushButton("Push", self)
self.cmd_button.clicked.connect(self.send_evt)
self.statusBar()
self.show()
def worker(self, inval):
print "in worker, received '%s'" % inval
time.sleep(2)
return "%s worked" % inval
@coroutine
def send_evt(self, arg):
out = AsyncTask(self.worker, "test string")
out2 = AsyncTask(self.worker, "another test string")
QThread.sleep(3)
print("kicked off async task, waiting for it to be done")
val = yield out
val2 = yield out2
print ("out is %s" % val)
print ("out2 is %s" % val2)
out = yield AsyncTask(self.worker, "Some other string")
print ("out is %s" % out)
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
m = MainWindow()
sys.exit(app.exec_())
Output (when the button is pushed):
in worker, received 'test string'
in worker, received 'another test string'
kicked off async task, waiting for it to be done
out is test string worked
out2 is another test string worked
in worker, received 'Some other string'
out is Some other string worked
As you can see, `worker` gets run asynchronously in a thread whenever it gets
called via the `AsyncTask` class, but its return value can be `yield`ed
directly from `send_evt`, without needing to use callbacks.
The code uses the coroutine-supporting features (`generator_object.send`) of
Python generators, and a [recipe I found on
ActiveState](http://code.activestate.com/recipes/578634-pyqt-pyside-thread-
safe-callbacks-main-loop-integr/) that provides a child->main thread
communication mechanism, to implement some very basic coroutines. The
coroutines are quite limited: You can't return anything from them, and you
can't chain coroutine calls together. It's probably possible to implement both
of those things, but also probably not worth the effort, unless you really
need them. I haven't done much negative testing with this either, so
exceptions in workers and elsewhere may not be handled properly. What it
_does_ do well, though, is allow you to call methods in separate threads via
the `AsyncTask` class, and then `yield` a result from the thread when one is
ready, **without blocking the Qt event loop**. Normally this kind of thing
would be done with callbacks, which can be difficult to follow and is
generally less readable than having all the code in a single function.
You're welcome to use this approach if the limitations I mentioned are
acceptable to you, but this is really just a proof-of-concept; you would need
to do a whole bunch of testing before you think about put it into production
anywhere.
As you mentioned, Python 3.3 and 3.4 makes asynchronous programming easier
with the introduction of `yield from` and `asyncio`, respectively. I think
`yield from` would actually be quite useful here to allow chaining coroutines
(meaning have one coroutine call another and get a result from it). `asyncio`
has no PyQt4 event-loop integration, so it's usefulness is pretty limited.
Another option would be to drop the coroutine piece of this altogether and
just use the [callback-based inter-thread communication
mechanism](http://code.activestate.com/recipes/578634-pyqt-pyside-thread-safe-
callbacks-main-loop-integr/) directly:
import sys
import time
from qtasync import CallbackEvent # No need for the coroutine stuff
from PyQt4 import QtGui
from PyQt4.QtCore import QThread
class MyThread(QThread):
""" Runs a function in a thread, and alerts the parent when done.
Uses a custom QEvent to alert the main thread of completion.
"""
def __init__(self, parent, func, on_finish, *args, **kwargs):
super(MyThread, self).__init__(parent)
self.on_finished = on_finish
self.func = func
self.args = args
self.kwargs = kwargs
self.start()
def run(self):
try:
result = self.func(*self.args, **self.kwargs)
except Exception as e:
print "e is %s" % e
result = e
finally:
CallbackEvent.post_to(self.parent(), self.on_finished, result)
class MainWindow(QtGui.QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.initUI()
def initUI(self):
self.cmd_button = QtGui.QPushButton("Push", self)
self.cmd_button.clicked.connect(self.send)
self.statusBar()
self.show()
def customEvent(self, event):
event.callback()
def worker(self, inval):
print("in worker, received '%s'" % inval)
time.sleep(2)
return "%s worked" % inval
def end_send(self, cmd):
print("send returned '%s'" % cmd)
def send(self, arg):
t = MyThread(self, self.worker, self.end_send, "some val")
print("Kicked off thread")
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
m = MainWindow()
sys.exit(app.exec_())
Output:
Kicked off thread
in worker, received 'some val'
send returned 'some val worked'
This could get a bit unwieldy if you're dealing with a long callback chain,
but it doesn't rely on the more unproven `coroutine` code.
|
The system cannot find the file specified when calling copy from python
Question: Here's my copy.py:
from subprocess import call
call("copy p2.txt p3.txt")
If in command prompt I use
`copy p2.txt p3.txt` it copies fine.
but when I use `python copy.py` it gives me:
Traceback (most recent call last):
File "copy.py", line 2, in <module>
call("copy p2.txt p3.txt")
File "C:\Python27\lib\subprocess.py", line 493, in call
return Popen(*popenargs, **kwargs).wait()
File "C:\Python27\lib\subprocess.py", line 679, in __init__
errread, errwrite)
File "C:\Python27\lib\subprocess.py", line 896, in _execute_child
startupinfo)
WindowsError: [Error 2] The system cannot find the file specified
If I replace the python call to copy with xcopy, it works fine.
Why would this be?
Answer: When `subprocess.call()`ing a command like in a shell, you'll need to specify
[`shell=True`](https://docs.python.org/2/library/subprocess.html#using-the-
subprocess-module) as well.
from subprocess import call
call("copy p2.txt p3.txt", shell=True)
The reason you need to use `shell=True` in this case is that the `copy`
command in Windows is not actually an executable but a built-in command of the
shell (if memory serves right). `xcopy` on the other hand is a real executable
(in `%WINDIR%\System32`, which is usually in the `%PATH%`), so it can be
called outside of a `cmd.exe` shell.
In this particular instance, [`shutil.copy` or
`shutil.copy2`](https://docs.python.org/2/library/shutil.html#shutil.copy)
might be viable alternatives.
Please note that using `shell=True` can lead to security hazards, or as the
docs put it:
> Warning: Using `shell=True` can be a security hazard. See the warning under
> [Frequently Used
> Arguments](https://docs.python.org/2/library/subprocess.html#frequently-
> used-arguments) for details.
|
python imobiledevice module error
Question: i write simple python script to test imobiledevice module ... my script :
import imobiledevice
if __name__ == '__main__':
dev = imobiledevice.iDevice()
but always get error :
Traceback (most recent call last):
File "/home/abbas/Main/test.py", line 7, in <module>
import imobiledevice
File "plist.pxd", line 8, in init imobiledevice (imobiledevice.c:57051)
ImportError: /usr/local/lib/python2.7/dist-packages/plist.so: undefined symbol: plist_set_type
i compile last version of libimobiledevice from source ...
please help
Answer: This is definitely problem within the `imobiledevice`.
I would recommend to try compiling from some older (stable) version.
|
Raising exception during SQLite database connection in Python
Question: Here is my code snippet:-
import sqlite3
database = "sample.db"
def dbConnection(database):
try:
connection = sqlite3.connect(database)
db_cursor = connection.cursor()
db_cursor.execute("show tables;")
rows = db_cursor.fetchall()
for row in rows:
print row
connection.close()
except sqlite3.Error, e:
print "Error in connection",e
dbConnection("enb.db")
It is raising this exception:-
Error in connection near "show": syntax error
I can't see anything wrong with the syntax as I just want to view the tables
in the database. What could be the problem here?Thanks
Answer: "SHOW TABLES" is not supported by SQLite. It is valid for other databases such
as MySQL.
[SQLite sql reference](http://sqlite.org/lang.html)
[How to 'show tables' in SQLite](http://stackoverflow.com/questions/82875/how-
do-i-list-the-tables-in-a-sqlite-database-file)
|
QStatusBar message disappears on menu hover
Question: I have a very basic `QMainWindow` application that contains a `menubar` and a
`statusbar`. When I hover over the menu the status message disappears. More
precisely, the status message is cleared. I have no idea what is causing this
behavior but it's resulting in a very difficult workaround for what I hoped to
be trivial behavior.
This is problematic for the following reason: I can make the message permanent
by adding a `QLabel` widget to the `QStatusBar`, but then I get the awkward
border. I don't want the border. The only way I know how to remove the border
is via `QStatusBar.setStyleSheet()`. I am using a palette for my color scheme
as opposed to a stylesheet so modifying the stylesheet messes up other colors.
I also can't restore the original `statusBar QLabel` color when I make a
modification via the stylesheet. I'm not the best at using stylesheets.
Is there a way to prevent the menu interaction from clearing the status
message? If not, is there a way to remove the border from the StatusBar when
adding a QLabel widget while preserving my palette (maybe not via
stylesheets)?
#!/usr/bin/env python
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
class win(QMainWindow):
def __init__(self,parent=None):
super(win,self).__init__(parent)
self.menubar = QMenuBar(self)
self.fileMenu = QMenu("File")
self.exitAction = QAction("Exit",self)
self.fileMenu.addAction(self.exitAction)
self.menubar.addMenu(self.fileMenu)
self.statusBar().showMessage("Hello")
self.connect(self.exitAction,SIGNAL("triggered()"), self.close)
if __name__ == "__main__":
app = QApplication(sys.argv)
GUI = win()
GUI.show()
app.exec_()
Answer: Basically, each widget you hover over sets the status bar text to their
`statusTip` property even when that property is an empty string.
For `QMenu`, the text is stored in the `menuAction` action status tip, so, you
can have a text instead of just clearing the status bar with something like
this:
self.fileMenu.menuAction().setStatusTip("File Menu is hovered")
To prevent anything to change the status bar, you can probably install an
`eventFilter` on the status bar and filter out all `QStatusTipEvent`.
|
How to implement a strategy pattern with runtime selection of a method?
Question: **_Context_**
I'm trying to implement some variant of strategy pattern in Python 2.7. I want
to be able to instantiate a 'my_strategy' base class, but switch between
different implementations of a 'score' method at run-time. I will have many
common methods in 'my_strategy' but a bunch of 'score' implementations. The
**main** illustrates how I want to use it. Here the scoring implementation is
dummy of course.
**_What I tried (i.e. My code so far)_**
strategy.py:
from algo_one import *
#from algo_two import *
class my_strategy ( object ):
def __init__(self, candidate = ""):
self.candidate = candidate
self.method = 'default'
self.no = 10
self._algo = algo_one
def set_strategy(self, strategy='default'):
self.strategy = strategy
if self.strategy == 'algo_one':
self._algo = algo_one
elif self.strategy == 'algo_two':
# self._algo = algo_two
pass
else:
self._algo = None
def score(self, *args):
if len(args) > 0:
self.candidate = args[0]
self._algo.score(self.candidate)
if __name__ == "__main__":
s = my_strategy()
s.strategy = 'algo_one'
s.candidate = "hello world"
print s.score()
print s.score("hi")
# s.set_method('algo_two')
# print s.score("hi")
I want to save the selected strategy in some sort of private pointer to the
sub-class method.
algo_one.py:
from strategy import my_strategy
class algo_one ( my_strategy ):
def score(self, candidate):
return len(candidate)*self.no
I could have a class-less method, but later I'll need to access public
variables of the base class.
algo_two.py:
from strategy import my_strategy
class algo_two ( my_strategy ):
def score(self, candidate):
return len(candidate)*3
I have an empty **init**.py too.
**_The errors_**
**1.** in score self._algo.score(self.candidate)
> TypeError: unbound method score() must be called with algo_one instance as
> first argument (got str instance instead)
**2.** If I uncomment the import of the second strategy:
from algo_two import *
I get the following error.
> ImportError: cannot import name my_strategy
My guess is that I run into some sort of circular dependency.
**3.**
from algo_one import *
This is obviously not pretty (unable to detect undefined names), but if I
from algo_one import algo_one
I get
> ImportError: cannot import name algo_one
**_Question_**
I think the errors are intertwined and that my approach, as a whole, may be
flawed. If not just addressing the error, I'm looking for suggestions to
improve the design. Or any comment, really. Also I'm open to suggestions
regarding the title of this question. Thank you!
Answer: You make it much more complicated than it needs to be. Python functions are
first class objects so the simplest way to implement the strategy pattern in
Python is to pass a 'strategy' function to your "context" object (the one that
uses the strategy). The fine part is that any callable object (ie: any object
implementing the `__call__` method) will work.
def default_score_strategy(scorer):
return len(scorer.candidate) * 3
def universal_answer_score_strategy(scorer):
return 42 # definitly the universal answer <g>
class ComplicatedStrategy(object):
def __init__(self, factor):
self.factor = factor
def __call__(self, scorer):
return len(scorer.candidate) * self.factor
class Scorer(object):
def __init__(self, candidate="", strategy=default_score_strategy):
self.candidate = candidate
self.strategy = strategy
def score(self):
return self.strategy(self)
s1 = Scorer("foo")
s2 = Scorer("bar", strategy=universal_answer_score_strategy)
s3 = Scorer("baaz", strategy=ComplicatedStrategy(365))
Note that your strategies dont have to be in the same module as the `Scorer`
class (well, except the default one of course), and that the module containing
the `Scorer` class doesn't have to import the stratgeies modules - nor know
anything about where the strategies are defined:
# main.py
from mylib.scores import Scorer
from myapp.strategies import my_custom_strategy
s = Scorer("yadda", my_custom_strategy)
|
Issues reading json from txt file
Question: I have a json string in a txt file and I'm trying to read it to do some other
procedures afterwards. It looks like this:
with open('code test.txt', 'r', encoding=('UTF-8')) as f:
x = json.load(f)
I know the json is valid, but I'm getting:
Traceback (most recent call last):
File "C:\Python33\lib\json\decoder.py", line 368, in raw_decode
obj, end = self.scan_once(s, idx)
StopIteration
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\Users\rodrigof\Desktop\xml test\xml extraction.py", line 334, in <module>
user_input()
File "C:\Users\rodrigof\Desktop\xml test\xml extraction.py", line 328, in user_input
child_remover()
File "C:\Users\rodrigof\Desktop\xml test\xml extraction.py", line 280, in child_remover
x = json.load(f)
File "C:\Python33\lib\json\__init__.py", line 274, in load
parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
File "C:\Python33\lib\json\__init__.py", line 319, in loads
return _default_decoder.decode(s)
File "C:\Python33\lib\json\decoder.py", line 352, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "C:\Python33\lib\json\decoder.py", line 370, in raw_decode
raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded
I used this [website](http://jsonlint.com/) to check if the string is valid.
If I use `.loads()`, I get a different error:
Traceback (most recent call last):
File "C:\Users\rodrigof\Desktop\xml test\xml extraction.py", line 334, in <module>
user_input()
File "C:\Users\rodrigof\Desktop\xml test\xml extraction.py", line 328, in user_input
child_remover()
File "C:\Users\rodrigof\Desktop\xml test\xml extraction.py", line 280, in child_remover
x = json.loads(f)
File "C:\Python33\lib\json\__init__.py", line 319, in loads
return _default_decoder.decode(s)
File "C:\Python33\lib\json\decoder.py", line 352, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer
Originally the json was embeded in my script like this:
json_text="""json stuff here"""
And didn't get any errors. Any ideas on how to fix this???
Running python 3.3.3 just in case.
Thanks!!
**EDIT:**
Just some random (valid) json on the txt and I get the same issue. This os one
of the ones i tried:
{"data":
{"mobileHelp":
{"value":
{
"ID1":{"children": [1,2,3,4,5]},
"ID2":{"children": []},
"ID3":{"children": [6,7,8,9,10]}
}
}
}
}
Which is valid as well as per jsonlint.com.
Answer: Your file contains a [UTF-8 BOM
character](http://en.wikipedia.org/wiki/Byte_order_mark#UTF-8) at the start.
UTF-8 **doesn't need a BOM** but especially Microsoft tools insist on adding
one anyway.
Open the file with the `utf-8-sig` encoding instead:
>>> open('/tmp/json.test', 'wb').write(b'\xef\xbb\xbf{"data":\r\n {"mobileHelp":\r\n {"value":\r\n {\r\n "ID1":{"children": [1,2,3,4,5]},\r\n "ID2":{"children": []},\r\n "ID3":{"children": [6,7,8,9,10]}\r\n }\r\n }\r\n }\r\n}')
230
>>> import json
>>> with open('/tmp/json.test', encoding='utf8') as f:
... data = json.load(f)
...
Traceback (most recent call last):
File "/Users/mj/Development/Library/buildout.python/parts/opt/lib/python3.3/json/decoder.py", line 367, in raw_decode
obj, end = self.scan_once(s, idx)
StopIteration
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
File "/Users/mj/Development/Library/buildout.python/parts/opt/lib/python3.3/json/__init__.py", line 271, in load
parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
File "/Users/mj/Development/Library/buildout.python/parts/opt/lib/python3.3/json/__init__.py", line 316, in loads
return _default_decoder.decode(s)
File "/Users/mj/Development/Library/buildout.python/parts/opt/lib/python3.3/json/decoder.py", line 351, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/Users/mj/Development/Library/buildout.python/parts/opt/lib/python3.3/json/decoder.py", line 369, in raw_decode
raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded
>>> with open('/tmp/json.test', encoding='utf-8-sig') as f:
... data = json.load(f)
...
>>> data
{'data': {'mobileHelp': {'value': {'ID2': {'children': []}, 'ID3': {'children': [6, 7, 8, 9, 10]}, 'ID1': {'children': [1, 2, 3, 4, 5]}}}}}
Note that from Python 3.4 onwards you get a more helpful error message here:
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
File "/Users/mj/Development/Library/buildout.python/parts/opt/lib/python3.4/json/__init__.py", line 268, in load
parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
File "/Users/mj/Development/Library/buildout.python/parts/opt/lib/python3.4/json/__init__.py", line 314, in loads
raise ValueError("Unexpected UTF-8 BOM (decode using utf-8-sig)")
ValueError: Unexpected UTF-8 BOM (decode using utf-8-sig)
|
kivy custom widget bind error
Question: I am new to Kivy as well as Python, so please bare with me. I am trying to
make a small tetris game for learning python with kivy. I am trying to create
a custom widget with size 20,20. When I add it to the float layout and run the
below code I receive the following error:
Error:
File "D:\OS Files\workspace\Tetris\holder.py", line 10, in __init__ self.add_widget(c)
File "C:\Kivy180\kivy\kivy\uix\floatlayout.py", line 115, in add_widget pos_hint=self._trigger_layout)
TypeError: descriptor 'bind' of 'kivy._event.EventDispatcher' object needs an argument
Code: holder.py File:
from items import Cell
class Holder(FloatLayout):
def __init__(self, **kwargs):
super(Holder,self).__init__(**kwargs)
self.size=(300,300)
c=Cell
#c.pos= (20,20)
self.add_widget(c)
#self.add_widget(c)
items.py File:
from kivy.uix.widget import Widget
from kivy.graphics import *
class Cell(Widget):
def __init__(self, **kwargs):
super(Cell,self).__init__(**kwargs)
with self.canvas:
Color(1, 0, 0)
Rectangle(pos=(0, 0), size=(50, 50))
self.height=50
self.width=50
main.py File:
from kivy.app import App
from holder import Holder
class start(App):
def build(self):
return Holder()
if __name__ == '__main__':
start().run()
Could you please explain where I went wrong, I am stuck at the starting point
itself. Regarding the error, I haven't written any events also, and it is just
a widget class. Could you please explain where I went wrong in understanding
kivy.
Answer:
c=Cell
I bet you want `c` to be an instance of the `Cell` class. If you want to do
that, you need to do:
c=Cell()
|
local variable 'moodsc' referenced before assignment
Question: In the code below I get the following error:
"local variable 'moodsc' referenced before assignment"
I'm new to programming and python. I'm struggling with interpreting other
questions on the similar topic. Any context around this specific code would be
helpful.
import re
import json
import sys
def moodScore(sent, myTweets):
scores = {} # initialize an empty dictionary
new_mdsc = {} # intitalize an empty dictionary
txt = {}
for line in sent:
term, score = line.split("\t") # The file is tab-delimited. "\t" means "tab character"
scores[term] = int(score) # Convert the score to an integer.
data = [] # initialize an empty list
for line in myTweets:
tweet = json.loads(line)
if "text" in tweet and "lang" in tweet and tweet["lang"] == "en":
clean = re.compile("\W+")
clean_txt = clean.sub(" ", tweet["text"]).strip()
line = clean_txt.lower().split()
moodsc = 0
pos = 0
neg = 0
count = 1
for word in range(0, len(line)):
if line[word] in scores:
txt[word] = int(scores[line[word]])
else:
txt[word] = int(0)
moodsc += txt[word]
print txt
if any(v > 0 for v in txt.values()):
pos = 1
if any(v < 0 for v in txt.values()):
neg = 1
for word in range(0, len(line)): # score each word in line
if line[word] not in scores:
if str(line[word]) in new_mdsc.keys():
moodsc2 = new_mdsc[str(line[word])][0] + moodsc
pos2 = new_mdsc[str(line[word])][1] + pos
neg2 = new_mdsc[str(line[word])][2] + neg
count2 = new_mdsc[str(line[word])][3] + count
new_mdsc[str(line[word])] = [moodsc2, pos2, neg2, count2]
else:
new_mdsc[str(line[word])] = [moodsc, pos, neg, count]
def new_dict():
for val in new_mdsc.values():
comp = val[0] / val[3]
val.append(comp)
for key, val in new_mdsc.items():
print (key, val[4])
def main():
sent_file = open(sys.argv[1])
tweet_file = open(sys.argv[2])
moodScore(sent_file, tweet_file)
# new_dict()
if __name__ == '__main__':
main()
Answer: Ok @joshp, I think you need to globalise some variables, because the error is
'moodsc referenced before assignment', I think the code only gets as far as
`moodsc += txt[word]` but you may also have trouble with `pos` and `neg`.
Try `global moodsc` and `pos` etc. before you define `moodsc` and `pos` etc.
If this doesn't work try `global moodsc` before `moodsc += txt[word]` and so
forth, you may need to use global in both places for it to work, I often find
that this is needed in my code, to globalise it at definition and wherever
else you use it (at the start of each function and statement where it is
used).
|
The best way to open two files
Question: I need to open a file, read a line, hash it, and then save to a different
file. Should I open both text files at the beginning of my script, or should I
open each every time I save/read? I'm new to all this and I'm using python for
android for sl4a. This is my code so far:
import android
import hashlib
import time
name = 0
droid = android.Android()
name = raw_input("Enter a password to hash: ")
hash_object = hashlib.md5 (name)
print(hash_object.hexdigest())
time.sleep(2)
print name
f = open('name.txt', 'w',)
f.write(hash_object.hexdigest())
f.close()
Answer: If you want to read from the file `name.txt` and write to another:
with open('name.txt', 'r') as f, open('out.txt', 'w') as f1:
line = f.next() # get first line
hash_object = hashlib.md5 (line)
f1.write(hash_object.hexdigest()) # write to second file
|
raise class exception pass rock paper scissor game
Question: I have this hw here which I am currently stuck on. My professor provided the
class exception for us, but I was wondering is anyone can tell me how it works
and for some reason when I run this program I get this:
Traceback (most recent call last):
File "C:\Python34\lab3.1.py", line 32, in <module>
rps_game_winner(game_2)
File "C:\Python34\lab3.1.py", line 5, in rps_game_winner
raise WrongNumberOfPlayersError('Wrong number of players!')
WrongNumberOfPlayersError: Wrong number of players!
so wondering if someone can tell me what i did wrong or what i can do to make
this program better. ty to everyone
class WrongNumberOfPlayersError(Exception): pass
class NoSuchStrategyError(Exception): pass
def rps_game_winner(game):
if len(game) != 2:
raise WrongNumberOfPlayersError('Wrong number of players!')
return print ("A WrongNumberOfPlayers error has occurred. \n\n")
# Write the code for the NoSuchStratgyError
stop_words = ['R', 'P', 'S']
if stop_words not in game[0]:
raise NoSuchStrategyError('No such strategy!')
# Write the code to determine the winner
# Write the code to return a List with the winner's name and strategy
if ("R" in game[0]) and ("S" in game[1]):
return print (game[0], "wins since Rock beat Scissor\n\n")
elif ("P" in game[0]) and ("R" in game[1]):
return print (game[0], "wins since Paper beat Rock\n\n")
elif ("S" in game[0]) and ("P" in game[1]):
return print (game[0], "wins since Scissor beat Paper\n\n")
elif ("S" in game[1]) and ("P" in game[0]):
return print (game[1], "wins since Scissor beat Paper\n\n")
elif ("P" in game[1]) and ("R" in game[0]):
return print (game[1], "wins since Paper beat Scissor\n\n")
elif ("R" in game[1]) and ("S" in game[0]):
return print (game[1], "wins since Rock beat Scissor\n\n")
game = [["Armando", "P"], ["Dave", "S"]]# ["Dave", "S"] wins
game_2 = [['Joe','R']] # wrong number of players
game_3 = [['Joe','R'],['Walter','Q']] # no such strategy as 'Q'
rps_game_winner(game)# returns the list ["Dave", "S"] wins since Scissors beat Paper
rps_game_winner(game_2)# raises exception wrong number of players
rps_game_winner(game_3)# raises exception no such strategy as 'Q'
Answer: I think you're having trouble understanding what an exception (or rather, an
`Exception`!) is. You define them for the purpose of understanding why your
code may have failed. For example:
class WrongNumberOfPlayersError(Exception):
pass
This is an `Exception` (literally, as it inherits from `Exception` so it can
do everything an `Exception` can do) that you've defined to know when you've
got the wrong number of players! Therefore
players = [("Player 1", "S"), ("Player 2", "P"), ("Player 3", "R")]
rps_game_winner(players)
# this should raise an exception, since there are the WRONG NUMBER OF PLAYERS!
You handle these with `try/except` blocks (called `try/catch` in some
languages) as such:
while True:
players = get_players() # imagine a function that created this list,
# now you're looping over making a new one each
# time it's wrong
try:
rps_game_winner(players)
except WrongNumberOfPlayersError as e:
# handle the exception somehow. You only make it into this block if
# there are the wrong number of players, and it's already looping forever
# so probably just...
pass
else: # if there are no exceptions
break # get out of the infinite loop!!
In your `rps_game_winner` function, you have the following logic:
if len(game) != 2:
raise WrongNumberOfPlayersError("Wrong number of players!")
return print ("A WrongNumberOfPlayers error has occurred. \n\n")
This is why I think your understanding is slightly flawed. Once you `raise`
that exception, the function exits. It never reads the `return` line (which is
probably for the best since you can't `return` a print function, it's just
`None` for reasons that are outside the scope of this discussion. In Python 2
I believe this would cause your code to fail to run completely)
This of a function like a small machine that does Work for you ("Work" in this
case being some sort of computation, or running an algorithm, etc). Once the
machine finishes working, it `return`s the result of that Work. However if
something goes wrong, it should inform you that "Hey this isn't the result of
my work, this is Something Bad," so it `raise`s an exception instead.
Essentially: you can either `raise` if something goes wrong, or `return` if
everything goes right.
Note that there are more things wrong than this (e.g. you can NEVER throw a
`NoSuchStrategyError` with your current code) but that the basics of the issue
are in a misunderstanding of what exceptions are for.
Below is an overly abstracted bit of code that should accomplish what you want
it to. Keep in mind that I've purposely obfuscated some of the code so it's
unusable as a copy/paste. In particular, I'm rather proud of my implementation
of win/lose/draw :)
R = 0b001
P = 0b010
S = 0b100
class WrongNumberOfPlayersError(Exception): pass
class NoSuchStrategyError(Exception): pass
class RPSGame(object):
def __init__(self, *players):
try:
self.p1, self.p2 = players
# assume constructed as game('p1','p2')
except Exception:
try: self.p1, self.p2 = players[0]
# assume constructed as game(['p1','p2'])
except Exception:
raise WrongNumberOfPlayersError("Only two players per game")
# no more assumptions, raise that exception
def start(self):
print("{0.name} plays {0.human_choice} || {1.name} plays {1.human_choice}".format(
self.p1, self.p2))
def winner(p1, p2):
global R, P, S
wintable = {R: {R^S: 2, R^P: 1},
P: {P^R: 2, P^S: 1},
S: {S^P: 2, S^R: 1}}
resulttable = ["Draw","Lose","Win"]
return resulttable[wintable[p1.choice].get(p1^p2,0)] + " for {}".format(p1)
return winner(self.p1, self.p2)
class Player(object):
rhyme_to_reason = {R:"Rock", P:"Paper", S:"Scissors"}
def __init__(self, name, choice):
self.name = name
try: choiceU = choice.upper()
except AttributeError:
# choice is R, P, S not "R", "P", "S"
choiceU = choice
if choiceU not in ("R","P","S",R,P,S):
raise NoSuchStrategyError("Must use strategy R, P, or S")
choicetable = {"R":R,"P":P,"S":S}
self.choice = choicetable.get(choiceU,choiceU)
self.human_choice = Player.rhyme_to_reason[self.choice]
def __xor__(self, other):
if not isinstance(other, Player):
raise NotImplementedError("Cannot xor Players with non-Players")
return self.choice^other.choice
def __hash__(self):
return hash((self.name, self.choice))
def __str__(self):
return self.name
if __name__ == "__main__":
import random, itertools
num_players = input("How many players are there? ")
players = [Player(input("Player name: "), input("Choice: ") or random.choice([R,P,S])) for _ in range(int(num_players))]
scoreboard = {player: 0 for player in players}
for pairing in itertools.combinations(players, 2):
game = RPSGame(pairing)
result = game.start()
if result.startswith("W"):
scoreboard[pairing[0]] += 1
elif result.startswith("L"):
scoreboard[pairing[1]] += 1
else:
pass
print(result)
for player, wins in scoreboard.items():
print("{:.<20}{}".format(player,wins))
|
Python smtplib: Why is the connection refused?
Question: So, in the Python interpreter, I do this (and only this):
>>> import smtplib
>>> s=smtplib.SMTP("localhost")
And this is what I get:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.4/smtplib.py", line 242, in __init__
(code, msg) = self.connect(host, port)
File "/usr/lib/python3.4/smtplib.py", line 321, in connect
self.sock = self._get_socket(host, port, self.timeout)
File "/usr/lib/python3.4/smtplib.py", line 292, in _get_socket
self.source_address)
File "/usr/lib/python3.4/socket.py", line 509, in create_connection
raise err
File "/usr/lib/python3.4/socket.py", line 500, in create_connection
sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused
Does anyone have any ideas as to why am I getting this error? (That's my
question.) It's not supposed to do that from what I understand. Tell me if I'm
wrong.
I'm using Xubuntu 14.04. If you need more information, please ask. I don't
know of anything else I can tell you, off-hand.
Thanks!
Answer: SMTPlib is going to try to connect to an SMTP service, usually running on port
25, though it can run on various other ports. Sounds like maybe you need to
install sendmail, postfix, or something of that nature.
|
Django urls regex is not working
Question: I have an issue with Django's urls.py's regex part. I want to show a page for
every entry users entered. My views.py looks like:
def tekent(request):
tumentry = Entry.objects.get(id=id)
return render_to_response("baslik/tekentry.html", locals(), context_instance=RequestContext(request))
def tek(request, slug):
basliklar = Baslik.objects.filter(active=True).order_by('-updated')
baslik = Baslik.objects.get(slug=slug)
entryler = baslik.entry_set.all()
form2 = EntryForm(request.POST or None)
if form2.is_valid():
entry = form2.save(commit=False)
entry.baslik = baslik
entry.user = request.user
entry.save()
return HttpResponseRedirect('/entry/%s'%(entry.id))
return render_to_response("baslik/tek.html", locals(), context_instance=RequestContext(request))
My main urls.py(not the app's) looks like this:
from baslik import *
urlpatterns = patterns('',
url(r'^entry/(?P<Entry.id>)/$', 'tekent', name = "tek_entry"),
)
and when I add an entry on web browser, it raises an error like this:
DoesNotExist at /baslik/entry4/
Baslik matching query does not exist.
Request Method: GET
Request URL: http://127.0.0.1:8000/baslik/entry4/
Django Version: 1.6.5
Exception Type: DoesNotExist
Exception Value:
Baslik matching query does not exist.
Exception Location: /Users/malisit/Django/sozluk/lib/python2.7/site-packages/django/db/models/query.py in get, line 310
Python Executable: /Users/malisit/Django/sozluk/bin/python
What should I do to fix this up? Thanks.
Answer: Try `url(r'^entry/(?P<id>\d+)/$', 'tekent', name = "tek_entry"),`
Why don't you use class based views?
[DetailView](https://docs.djangoproject.com/en/1.6/ref/class-based-
views/generic-display/#detailview) is really handy for such things.
|
Tkinter Button will not create due to error in function
Question: I am very new to Python and especially new to using Tkinter. I have a question
on getting a button of mine to actually create in the GUI.
I am trying to make a basic button that will take an input from an entry box
as an integer and add it to the current balance (kind of a little bank app).
The problem is that when I run the code and click the deposit button, the
second "Make Deposit" button that is supposed to spawn in (defined in the
make_deposit() function) will not spawn in due to an error in turning the
input for the entry box into an integer. As far as I can tell, this error is
only created because the second "Make Deposit" button is trying to run its
function before the button is pressed. Is there any way to prevent this from
happening? Below is the code, excluding some bits of the program not relevant
to the issue at hand.
from Tkinter import *
def get_entry(entry):
global s
s = entry.get()
s = int(s)
data["current"] += s
label = Label(root, text = "Current Balance: %d" % (data["current"]))
label.grid(row = 1, column = 0)
def make_deposit():
deposit = Entry(root, text = "Deposit Amount")
deposit.grid(row = 2, column = 0)
withdrawal.grid_forget()
deposit_button = Button(root, text = "Make Deposit", command = get_entry(deposit))
deposit_button.grid(row = 3, column = 0)
frame = Frame(root, height = 300, width = 300)
frame.grid(row = 1, column = 0)
label = Label(root, text = "ETA Until Car Purchase")
label.grid(row = 0, column = 0)
label = Label(root, text = "Current Balance: %d" % (data["current"]))
label.grid(row = 1, column = 0)
deposit = Button(root, text = "Make Deposit", command = make_deposit)
deposit.grid(row = 2, column = 0)
withdrawal = Button(root, text = "Make Withdrawal")
withdrawal.grid(row = 3, column = 0)
Any help would be greatly appreciated, and please take into account that I am
an absolute beginner to Tkinter so the way that I have created some of the GUI
elements might not be the best way of doing so.
Answer: `command=` expect function name without `()` and arguments.
Using
command = get_entry(deposit)
You run function `get_entry(deposit)` and its result is assigned to
`command=`.
It is good if you want to assign function to `command=` dynamicly.
But you need `lambda`:
command = lambda: get_entry(deposit)
|
Simple Python POST urlencode()
Question: I'm trying to send a POST to my Node.js app using Python. Here is my code
import urllib
import urllib2
url = my_url
values = {'email' : my_email,
'password' : my_password }
data = urllib.urlencode(values)
req = urllib2.Request(url,data)
response = urllib2.urlopen(req)
the_page = response.read()
print(the_page)
The request is sent, but somehow the parameters are getting messed up because
the response I am getting corresponds to invalid login credentials.
I can do this same request using Postman for Chrome and it works just fine. So
I know it's not something with my API.
So essentially I can do GET requests just fine with Python but for some
reason, when I try to include parameters in a POST they are not translated
correctly.
I've already looked through the docs for urllib, urllib2 and urlencode(). I
could not find anything helpful
Answer: I do no longer debug urllib2 problems, since I switched to requests, I do no
longer have them, you may do so:
import requests
print requests.post(my_url, data={'email': my_email, 'password': my_password}).text
So readable, so elegant... If your jquery app returns json, you may use
".json()" instead of ".text"
Your problem seems to have to keep cookies, to do so, you may just use a
[requests session](http://docs.python-requests.org/en/latest/user/advanced/)
|
Enums in SQLite
Question: My model uses a couple of Enum's for various columns, creating the tables
using SQLAlchemy's create_all() method works fine in PostgreSQL, but it
doesn't work with SQLite, it just stalls.
The problem seems to be with creating Enum's, as far as I can tell sqlite
doesn't support these, but according to SQLAlchemy's docs that shouldn't pose
a problem. When I try to create_all() on an sqlite memory db it just stalls,
even with echo=True no output appears.
I tried the following code to demonstrate the problem:
from sqlalchemy import create_engine, Enum
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
e = Enum('foo', 'bar', metadata=Base.metadata)
engine = create_engine('sqlite:///:memory:', echo=True)
Base.metadata.create_all(bind=engine)
When I run this script it shows no output whatsoever, it just stalls. Python
uses 100% CPU and the script never ends, until I ctrl-c it.
When I try to create_all() on my actual schema it does echo some PRAGMA
commands trying to determine if tables exist, but then it stalls on the
creating the Enums. I tried to remove code from the model definition until it
worked just fine, this was when I figured out it's the Enums.
I tried to run this on Python 3.4 with SQLAlchemy 0.9.6 using SQLite 3.7.13.
Answer: A friend ran into exactly this same problem recently, and it looks to me like
an infinite-loop bug in SQLA (which I should really report, so thanks for this
minimal testcase :)).
Just remove the `metadata=` kwarg from your real code; as long as the enum is
used as a type inside a declarative class, it'll inherit the right metadata
anyway.
|
Different versions of django
Question: I have just moved my django application to another server, which I have
configured a long time ago, so I'm not really sure what's installed and
configured. When running the application, I started getting weird errors,
which pointed to running an old version of django. Hence, I decided to check
the version.
First, I ran:
python -c "import django; print(django.get_version())"
which showed version **1.3.1**. So then I did
sudo easy_install --upgrade django
which ran fine, but when running the first command again, it still shows
**1.3.1** , so I decided to do:
django-admin.py version
and this returned **1.6.5**. Therefore, I assume that I have installed the
latest django version, but for some reason python is using **1.3.1**.
**How can I get python to use the latest version of django?**
Answer: Firstly do not use `easy_install` but `pip`:
easy install pip
Try to install/update from `pip`:
pip install django --upgrade
If it fails, try to uninstall and after réinstall:
pip uninstall django
Be careful if you've installed django with Ubuntu's `apt-get`. It's a bad
thing to mix system and python installers. Uninstall from `apt-get` if it's
the case:
apt-get remove python-django
|
lldb python handle breakpoint hit
Question: I was looking through this huge LLDB python reference manual, and can't find
still how to handle breakpoint hit with my code. I mean, I want to run my
foo() when some breakpoint was hit.
Please help me with some code snippets!
Or point me the needed class in Python reference manual.
Thanx!
Answer: On the page:
<http://lldb.llvm.org/python-reference.html>
there is a section titled:
RUNNING A PYTHON SCRIPT WHEN A BREAKPOINT GETS HIT
which has some useful info.
What you are doing is "adding a command to your breakpoint". The lldb command
for this is "breakpoint command add". All the basic lldb commands are in the
form "noun [sub-noun [...]] verb options"; knowing that might help translate
from the thing you want to do to where in the command set the command for that
operation lives. Anyway, the help on "breakpoint command add" has other
examples that might be useful.
Then condensed version is, make a python module containing a function with
this signature:
breakpoint_function (frame, bp_loc, dict)
Bring that module into lldb with the command:
(lldb) command script import "path to your .py file"
You can also use the module name in "command script import" if you've set up
the PYTHONPATH to point to it, but unlike Python's "import" you don't have to,
the command will take care of that for you.
Then make a breakpoint, and use "br com a" to add your function to it:
(lldb) br com a -F MyModule.breakpoint_function
Now when a breakpoint gets hit, your function will get called with the
following arguments:
The "frame" argument is the frame that hit the breakpoint. You can get the
thread from the frame & thus the complete stack if you need it.
The "bploc" argument is the "Breakpoint Location" that hit the breakpoint. In
lldb one "breakpoint specification" (which is what you are setting with "break
set") can resolve to many locations. For instance, a "source pattern"
breakpoint might match many source patterns in your code. So you might want to
know which one was actually hit.
The "dict" option is so we can squirrel some stuff away and pass it to Python,
it should be left alone.
One other thing to keep in mind is that though the script interpreter
(accessible with the "script" command) defines lldb.thread, lldb.frame etc.
convenience variables, these variables are NOT set up when your breakpoint
command is running. So if you've used these variables in the script
interpreter while prototyping your command, you'll have to find them from the
frame you were passed in if you need them in the breakpoint command.
Note, Python breakpoint commands don't currently work in Xcode 6, though that
should be fixed by the time it is done.
|
Where are python logs default stored when ran through IPython notebook?
Question: In an IPython notebook cell I wrote:
import logging
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)
handler = logging.FileHandler('model.log')
handler.setLevel(logging.INFO)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
logger.addHandler(handler)
Notice that I am supplying a file name, but not a path.
Where could I find that log? (ran a 'find' and couldn't locate it...)
Answer: There's multiple ways to set the IPython working directory. If you don't set
any of that in your IPython profile/config, environment or notebook, the log
should be in your working directory. Also try `$ ipython locate` to print the
default IPython directory path, the log may be there.
What about giving it an absolute file path to see if it works at all?
Other than that the call to `logging.basicConfig` doesn't seem to do anything
inside an IPython notebook:
# In:
import logging
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger()
logger.debug('root debug test')
There's no output.
As per the docs, the
[`logging.basicConfig`](https://docs.python.org/2/library/logging.html#logging.basicConfig)
doesn't do anything if the root logger already has handlers configured for it.
This seems to be the case, IPython apparently already has the root logger set
up. We can confirm it:
# In:
import logging
logger = logging.getLogger()
logger.handlers
# Out:
[<logging.StreamHandler at 0x106fa19d0>]
So we can try setting the root logger level manually:
import logging
logger = logging.getLogger()
logger.setLevel(logging.DEBUG)
logger.debug('root debug test')
which yields a formatted output in the notebook:
Now onto setting up the file logger:
# In:
import logging
# set root logger level
root_logger = logging.getLogger()
root_logger.setLevel(logging.DEBUG)
# setup custom logger
logger = logging.getLogger(__name__)
handler = logging.FileHandler('model.log')
handler.setLevel(logging.INFO)
logger.addHandler(handler)
# log
logger.info('test info my')
which results in writing the output both to the notebook and the _model.log_
file, which for me is located in a directory I started IPython and notebook
from.
Mind that repeated calls to this piece of code without restarting the IPython
kernel will result in creating and attaching yet another handler to the logger
on every run and the number of messages being logged to the file with each log
call will grow.
|
python and global variables
Question: How do I setup the global variable properly?
# default objects is being set as None (null), after importing the piCamera library
camera = None
after that I'm declaring the Webcam class with the `GET` definition:
class Webcam:
def GET(self):
web.header('Content-type','multipart/x-mixed-replace; boundary=--jpgboundary')
stream=io.BytesIO()
start=time.time()
for foo in camera.capture_continuous(stream,'jpeg'):
web.header('Content-type','--jpgboundary')
web.header('Content-type','image/jpeg')
web.header('Content-length',len(stream.getvalue()))
yield (stream.getvalue())
stream.seek(0)
stream.truncate()
time.sleep(.5)
if __name__ == "__main__":
camera = picamera.PiCamera()
global camera
camera.resolution = (640, 480)
app = web.application(urls, globals())
app.internalerror = web.debugerror
app.run()
Should I put the `if __name__ == "__main__":` before I'm defining the Webcam
class?
Here's my traceback of the calls:
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/wsgiserver/__init__.py", line 1245, in communicate
req.respond()
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/wsgiserver/__init__.py", line 775, in respond
self.server.gateway(self).respond()
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/wsgiserver/__init__.py", line 2018, in respond
response = self.req.server.wsgi_app(self.env, self.start_response)
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/httpserver.py", line 306, in __call__
return self.app(environ, xstart_response)
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/httpserver.py", line 274, in __call__
return self.app(environ, start_response)
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/application.py", line 281, in wsgi
result = peep(result)
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/application.py", line 261, in peep
firstchunk = iterator.next()
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/application.py", line 605, in wrap
yield next()
File "/usr/local/lib/python2.7/dist-packages/web.py-0.37-py2.7.egg/web/application.py", line 597, in next
return result.next()
File "/home/pi/piApp/index.py", line 77, in GET
for foo in camera.capture_continuous(stream,'jpeg'):
AttributeError: 'NoneType' object has no attribute 'capture_continuous'
Answer: It looks like you are running this as a library file and therefore the
`__main__` section does not execute. Put that code at global scope.
I would guess something like this is what you want:
def main():
global camera
camera = picamera.PiCamera()
camera.resolution = (640, 480)
app = web.application(urls, globals())
app.internalerror = web.debugerror
app.run()
main()
|
Does ply.lex parse the same token once?
Question: I was reading a [lexical parsing](http://www.dabeaz.com/ply/ply.html) document
so that I can parse some arguments and I exactly followed the document to
create a parser. This is the whole code:
#!/usr/bin/env python
#-*- coding: utf-8 -*-
import ply.lex as lex
args = ['[watashi]', '[anata]>500', '[kare]>400&&[kare]<800']
tokens = ('NUMBER', 'EXPRESSION', 'AND', 'LESS', 'MORE')
t_EXPRESSION = r'\[.*\]'
t_AND = r'&&'
t_LESS = r'<'
t_MORE = r'>'
t_ignore = '\t'
def t_NUMBER(t):
r'\d+'
t.value = int(t.value)
return t
def t_newline(t):
r'\n+'
t.lexer.lineno += len(t.value)
def t_error(t):
print 'Illegal character "%s"' % t.value[0]
t.lexer.skip(1)
lexer = lex.lex()
for i in args:
lexer.input(i)
while True:
tok = lexer.token()
if not tok: break
print tok
print '#############'
I simply created a list of sample arguments and I got this output:
LexToken(EXPRESSION,'[watashi]',1,0)
#############
LexToken(EXPRESSION,'[anata]',1,0)
LexToken(MORE,'>',1,7)
LexToken(NUMBER,500,1,8)
#############
LexToken(EXPRESSION,'[kare]>400&&[kare]',1,0)
LexToken(LESS,'<',1,18)
LexToken(NUMBER,800,1,19)
#############
The first and second sample arguments are parsed correctly, but the third one
is not. The third sample argument is EXPRESSION+LESS+NUMBER whereas it must be
EXPRESSION+MORE+NUMBER+AND+EXPRESSION+LESS+NUMBER. So I thought there could be
one of those problems:
* **ply.lex is only parsing one token:** In the codes above, ply.lex cannot parse two seperate expressions and it returns the latest token as its type. "[kare]>400&&[kare]" is EXPRESSION because it ends with the latest EXPRESSION token which is second [kare] and 800 is NUMBER because it is the latest NUMBER token.
**!!! OR !!!**
* **There is a mistake in t_EXPRESSION variable:** I defined this variable as "[.*]" to get all characters in those two brackets ([]). The first token of third sample argument is "[kare]>400&&[kare]" since it simply starts and ends with those brackets and contains .* (every single character) in them, but I thought the interpreter would stop in the first (]) character due to being first.
So I could not find a way to solve but asked here.
in general this is what I am struggling with
lexer.input("[kare]>400&&[kare]<800")
while True:
tok = lexer.token()
if not tok: break
print tok
I get
LexToken(EXPRESSION,'[kare]>400&&[kare]',1,0)
LexToken(LESS,'<',1,18)
LexToken(NUMBER,800,1,19)
but I expected something more like
LexToken(EXPRESSION,'[kare]',1.0)
LexToken(LESS,'>',?)
LexToken(NUMBER,400,?)
LexToken(AND,'&&',?)
LexToken(EXPRESSION,'[kare]',1,0)
LexToken(LESS,'<',1,18)
LexToken(NUMBER,800,1,19)
Answer: I think I see your problem
t_EXPRESSION = r'\[.*\]'
is greedy and will match the biggest match it can ie `'[kare]>400&&[kare]'`
instead try
t_EXPRESSION = r'\[[^\]]*\]'
this will match only one set since it looks for not open bracket(`[^\]]`)
instead of anything(`.`)
you can also use not greedy matching
t_EXPRESSION = r'\[.*?\]'
the `?` makes it match as few characters as possible rather than the maximum
|
How can I make the composite of two images in OpenCV with Python?
Question: I have one image that remains unchanged and another image which is the first
one, but with a filter applied on it. I want to create the third image which
should be the composite of these first two images.
I know that in MATLAB there is a function called as `imfuse()` with the
default color channel green-magenta. I want to do the same thing in Python,
with exactly the same color channel. How can I do this ?
Here are the images (first is the original picture, second is the first
picture with the filter applied, third is the MATLAB result):
Thanks for your help !
Answer: By default, [`imfuse`](http://www.mathworks.com/help/images/ref/imfuse.html)
simply overlays the pair of images in different color bands (Default being
`Method=falsecolor` and `ColorChannels=green-magenta`).
Here is an example in MATLAB to illustrate (it should should be easy to write
this in Python/OpenCV):
% a pair of grayscale images
A = imread('cameraman.tif');
B = imrotate(A,5,'bicubic','crop'); % image "A" rotated a bit
% use IMFUSE
C = imfuse(A,B);
imshow(C)
% use our version where: Red=B, Green=A, Blue=B
C = cat(3, B, A, B);
imshow(C)
Both should give you the same thing:
* * *
# EDIT:
Here is the Python/OpenCV version:
import numpy as np
import cv2
A = cv2.imread(r"C:\path\to\a.png", 0)
B = cv2.imread(r"C:\path\to\b.png", 0)
#C = cv2.merge((B,A,B))
C = np.dstack((B,A,B))
cv2.imshow("imfuse",C)
cv2.waitKey(0)
|
Python - change pixel value
Question: I have used this code to change the pixel value of image,
im=Image.open("image.jpg")
pix=im.load()
pix[50,50]=(70,70,70)
it is work well with me, but when I use a png image everything is okay and the
changes are saved to the image, but when I use a JPG image the changes are not
saved to the image. Is there something missing in the code, do I need to save
the changes , and how would I do ??
Answer: Try with:
im.putpixel((50,50), (70, 70, 70))
or you can also do:
import numpy as np
from PIL import Image
# pix has 4 channels for png and 3 for jpg
pix = np.array(im)
pix[50, 50, 0] = 70 # 0 accesses the first channel
pix[50, 50, 1] = 70 # 1 accesses the second channel
pix[50, 50, 2] = 70 # 2 accesses the third channel
Image.fromarray(pix).save('new_img.jpg')
|
How can I make Python's ElementTree enforce XML schema?
Question: Suppose I wish to parse an XML document, and its schema dictates that a given
element can only occur once.
How do I make sure that an exception gets raised if the element occurs twice
or more?
Or, if the schema says that a given element's value should be an integer, and
the value is "turkey sandwich", how do I make the parser crash and burn like
it's supposed to?
Can ElementTree do this? Can anything do this? Does this question even make
sense?
Answer: ElementTree from the STD lib has not schema support. For this, I suggest you
to use the [lxml](http://lxm.de/) package which has it (and by the way, it's
much faster).
Here after an example from my own code:
from lxml import etree
# Create the schema object
with open(xsd_file) as f:
xmlschema_doc = etree.parse(f)
xmlschema = etree.XMLSchema(xmlschema_doc)
# Create a tree for the XML document
doc = etree.parse(xml_text)
# Validate the XML document using the schema
return xmlschema.validate(doc)
or if you want a exception to be raised:
xmlschema.assertValid(doc)
|
Getting an error for a simple Tkinter program
Question: I have been trying to make a simple program using Tkinter and Python. All you
do is click buttons and depending on what button you click, it updates certain
labels. This is my code:
from tkinter import *
apples = 0
gold = 0
def pick():
global apples
apples = apples + 1
def sell():
global apples
global gold
gold = gold + (apples * 10)
apples = 0
app = Tk()
app.title("Apple Picking Simulator 2014")
app.geometry("400x300+100+60")
label1 = Label(text = "Welcome to Apple Picking Simulator 2014!").pack()
Label().pack()
label2 = Label(text = "Apples: " + apples).pack()
label3 = Label(text = "Gold: " + gold).pack()
button1 = Button(text = "Pick Apple", command = pick).pack()
button2 = Button(text = "Sell Apples", command = sell).pack()
app.mainloop()
Now, whenever I try to run the program, I just get the error:
TypeError: Can't convert 'int' object to str implicitly
I understand that it can't convert an integer to a string, but I've been
trying everything, and I can't seem to make it work. Is there an easy way to
display the apple and gold numbers on the window and have them update every
time I click the pick or sell button? Thanks.
Answer: Trying to concatenate an integer to a string is what is causing your error.
You need to explicitly cast your `apples` and `gold` integer variables to a
string using the [`str`
function](https://docs.python.org/2/library/functions.html#str).
Replace:
label2 = Label(text = "Apples: " + apples).pack()
label3 = Label(text = "Gold: " + gold).pack()
With:
label2 = Label(text = "Apples: " + str(apples)).pack()
label3 = Label(text = "Gold: " + str(gold)).pack()
Fixed source code:
from tkinter import *
apples = 0
gold = 0
def pick():
global apples
apples = apples + 1
def sell():
global apples
global gold
gold = gold + (apples * 10)
apples = 0
app = Tk()
app.title("Apple Picking Simulator 2014")
app.geometry("400x300+100+60")
label1 = Label(text = "Welcome to Apple Picking Simulator 2014!").pack()
Label().pack()
label2 = Label(text = "Apples: " + str(apples)).pack()
label3 = Label(text = "Gold: " + str(gold)).pack()
button1 = Button(text = "Pick Apple", command = pick).pack()
button2 = Button(text = "Sell Apples", command = sell).pack()
app.mainloop()
|
How to parse multiple expressions when using the rply library
Question: I created a parser using the rply library for python and can currently perform
basic arithmetic. The problem is that I cannot parse more than one line when
reading from a file. Say I have: 5 + 4 on a single line.
That parses with no errors. But if I have something like the following over
two lines.
5 + 4
7 * 3
I get this error: rply.errors.ParsingError.
I have set my lexer to ignore newlines and spaces:
lg.ignore('\n')
lg.ignore('\s+')
And these are my productions:
@pg.production('main : expression')
def main(p):
return p[0]
@pg.production(’expression : NUMBER’)
def expression_number(p):
return Number(int(p[0].getstr()))
@pg.production(’expression : expression PLUS expression’)
def expression_binop(p):
left = p[0]
right = p[2]
if p[1].gettokentype() == ’AND’:
return Add(left, right)
Any help would be greatly appreciated! Thanks!
Answer: This will work, you had no multiplication setup:
from rply import ParserGenerator, LexerGenerator
from rply.token import BaseBox
lg = LexerGenerator()
# Add takes a rule name, and a regular expression that defines the rule.
lg.add("PLUS", r"\+")
lg.add("MINUS", r"-")
lg.add("NUMBER", r"\d+")
lg.add('MUL', r'\*') # added MUL here
lg.ignore(r"\s+")
# This is a list of the token names. precedence is an optional list of
# tuples which specifies order of operation for avoiding ambiguity.
# precedence must be one of "left", "right", "nonassoc".
# cache_id is an optional string which specifies an ID to use for
# caching. It should *always* be safe to use caching,
# RPly will automatically detect when your grammar is
# changed and refresh the cache for you.
pg = ParserGenerator(["NUMBER", "PLUS", "MINUS",'MUL'], # added MUL here
precedence=[("left", ['PLUS', 'MINUS'])], cache_id="myparser")
@pg.production("main : expr")
def main(p):
# p is a list, of each of the pieces on the right hand side of the
# grammar rule
return p[0]
@pg.production("expr : expr MUL expr") # added MUL here
@pg.production("expr : expr PLUS expr")
@pg.production("expr : expr MINUS expr")
def expr_op(p):
lhs = p[0].getint()
rhs = p[2].getint()
if p[1].gettokentype() == "PLUS":
return BoxInt(lhs + rhs)
elif p[1].gettokentype() == "MINUS":
return BoxInt(lhs - rhs)
elif p[1].gettokentype() == 'MUL': # added Mul here
return BoxInt(lhs * rhs)
else:
raise AssertionError("This is impossible, abort the time machine!")
@pg.production("expr : NUMBER")
def expr_num(p):
return BoxInt(int(p[0].getstr()))
lexer = lg.build()
parser = pg.build()
class BoxInt(BaseBox):
def __init__(self, value):
self.value = value
def getint(self):
return self.value
with open("hello.txt") as f:
for line in f:
if line.strip():
print parser.parse(lexer.lex(line)).value
21
9
|
Removing integer values from a alphanumeric column in python
Question: I am new to python and struggling in one trivial task. I have one alphanumeric
column known as region. It has both entries beginning with / such as
/health/blood pressure etc and integer values. So typically few observations
look like:
/health/blood pressure
/health/diabetes
7867
/fitness
9087
/health/type1 diabetes
Now I want to remove all the rows/cases with integer values. So after
importing the data set into python shell, it is showing region as object. I
intended to solve this problem with a sort of regular expression. So I did the
following:
pattern='/'
data.region=Series(data.region)
matches=data.region.str.match(pattern)
matches
Here it gives a boolean object explaining whether each pattern is in the data
set or not. So I get something like this:
0 true
1 false
2 true
3 true
.........
so on.
Now I am stuck further how to remove rows of matches boolean object with false
tag. If statement is not working. If anyone can offer some sort of assistance,
that would be great!!
Thanks!!
Answer: It seems like you are using the pandas framework. So I am not completely sure
if this is working:
You can try:
matches = [i for i in data.region if i.str.match(pattern)]
In python this is called a list comprehension that goes through every entry in
data.region and checks your pattern and puts it in the list if the pattern is
matching (and the expression after 'if' is thus true).
See: <https://docs.python.org/2/tutorial/datastructures.html#list-
comprehensions>
If you want to map those for every region you can try to create a dictionary
that maps the regions to the lists with the following dict-comprehension:
matches = {region: [i for i in data.region if i.str.match(pattern)] for region in data}
See: <https://docs.python.org/2/tutorial/datastructures.html#dictionaries>
However you are definitely leaving the realm of the pandas framework. This
could eventually fail of regions is not an integer/string but a list itself
(as Is aid I don't know pandas enough to judge).
In that case you could try:
matches = {}
for region in list_of_regions:
matches[region] = [i for i in data.region if i.str.match(pattern)]
which is basically the same just with a given list of region and the dict
comprehension made explicit in a for loop.
|
How can I import an Odoo/OpenERP Addon module in an interactive python environment?
Question: How do I import an Odoo/OpenERP addon module from a python shell?
I want to learn more about the structure of Odoo. I prefer to do that through
IPython, but I'm not sure how to import addons into the environment. For
starts I merely want to load a default Addon into my environment. So I just
copied a line from the default Product module. I did not modify anything in
the source code. I have been grepping through the source code to find out why
I can't simply import the Addon in the I'm used to with Python.
My Odoo installation works fine.
$ cd /opt/odoo
$ ipython
In [1]: import openerp
In [2]: openerp.modules.module?
[not much luck]
In [3]: openerp.addons?
[not much luck either, nothing here either]
In [4]: import openerp.addons
[no error]
In [5]: import openerp.addons.decimal_precision as dp # Line from addons/product/product.py
[....]
ImportError: No module named decimal_precision
`openerp.addons` doesn't have anything but still `import openerp.addons.STUFF`
works fine from Odoo addon modules.
I have the feeling that `addons` needs to be initialized but I haven't found
out how to do that. I started going through the code from
`openerp.main.cli()`.
`openerp.tools.config.parse_config()` is a step in the right direction but
it's not enough. I need to somehow pass `--addons-path=addons` as well (since
Odoo is not smart enough to find its own addons).
Answer: According to [openerp source
code](https://github.com/odoo/odoo/blob/master/openerp/addons/__init__.py)
> Addons are made available under `openerp.addons` after
> openerp.tools.config.parse_config() is called (so that the addons paths are
> known).
so you should call `openerp.tools.config.parse_config()` before doing any
import.
If you need to pass any arguments you can do it as such:
`openerp.tools.config.parse_config(['--addons-path=addons'])`
|
How to cast variables in python with jcc
Question: In java it is possible to cast an object onto a class. An good example is
found here
Object aSentenceObject = "This is just a regular sentence";
String aSentenceString = (String)aSentenceObject;
I have a program that needs to integrate some java with python. I am trying to
do this via the [JCC library](https://pypi.python.org/pypi/JCC/). The problem
that I am encountering is that with JCC, all of the java classes are loaded
into the imported library that I created with JCC. So I can create an instance
of the base class by passing the necessary argument to the constructor of the
java class.
obj = javaLibrary.BaseClass('foo')
However, in my code I need to be able to cast this object onto a a more
“specific” type of Object. How can I accomplish this in python with JCC? It
seems like it may be impossible because python is dynamically typed, but that
is why I am asking this question.
Answer: All comments above valid, but to be specific for your case:
casted_obj = Object.cast_(obj)
|
Getting actual facebook and twitter image urls using python
Question: I want to write a python code that downloads 'main' image from urls that
contain images.
I have urls like these in my data (text files)
1. <http://t.co/fd9F0Gp1P1>
points to an fb image
1. <http://t.co/0Ldy6j26fb>
points to twitter image
but their expanded urls don't result in .jpg,.png images. Instead they direct
us to a page that contains the desired image.
How do I download images from these urls?
Answer: Here you will find an example of how I downloaded the plane image from the
facebook page, you can adapt this to work for your twitter page:
from bs4 import BeautifulSoup
import urllib
urlData = urllib.urlopen('https://www.facebook.com/photo.php?fbid=10152055005350906')
data = str(urlData.readlines())
bs = BeautifulSoup(data)
imgUrl = bs.find('img', attrs={'class': 'fbPhotoImage img'}).get('src')
urllib.urlretrieve(imgUrl, "plane.jpg")
## **EDIT**
I decided to actually help you out with the twitter one as well, here is the
twitter example of downloading the image from the link you gave:
from bs4 import BeautifulSoup
import urllib
urlData = urllib.urlopen('https://twitter.com/USABillOfRights/status/468852515409502210/photo/1')
data = str(urlData.readlines())
bs = BeautifulSoup(data)
imgUrl = bs.find('img', attrs={'alt': 'Embedded image permalink'}).get('src')
urllib.urlretrieve(imgUrl, "cnn.jpg")
And here is the web reference for
[BeautifulSoup.](http://www.crummy.com/software/BeautifulSoup/)
|
Hide os.system command line call in python script
Question: I have a python script (myscript.py) that I am running on the linux server
like below:
python myscript.py
In my script I am using the system call, example below:
os.system("./myprogram.pl -x 5 > results.out")
When I run myscript.py on the server whenever there is `os.system` call, the
command call is visible on the server. Is there a way to hide all the command
calls so that they are not displayed when they are called within the program
(`myscript.py`)? (This is not about hiding the output resulted in the command
calls within the program)
Answer: You can use a subprocess pipe instead of the os.system command:
import subprocess;
NewPipeObject = subprocess.Popen( [ './myprogram.pl -x 5 > results.out' ],
stdout= subprocess.PIPE,
stderr= subprocess.PIPE );
or you can take advantage of the list format of the arguments for the
subprocess pipe (it adds a space between each list element) and present them
as the following (which will be easier to generalize):
import subprocess;
NewPipeObject = subprocess.Popen( [ './myprogram.pl',
'-x',
'5',
'>',
'results.out' ],
stdout= subprocess.PIPE,
stderr= subprocess.PIPE );
Either way you're suppressing the outputs from `stdout` and `stderr` into the
pipe object (`NewPipeObject`).
|
python interactive shell using cmd repeating statements with no arguments typed
Question: New to python and i'm working on an interactive shell using cmd that takes
defined functions and arguments and returns value in an if/then format.
Example below. But my issue is that every time the user types a function and i
return something to the user, if they just hit enter then they recieve the
last provided output.
For example code below...but basically if the user doesn't type an argument or
function for that matter, i just want nothing displayed just a "" or empty
space. I assumed the else pass argument would have done that for me, but
obviously not. I have tried if and elif, with the same results.
Example output with "test arp", just hitting enter returns the previous
argument pressed :
user@hostname>test arp
? (192.168.50.1) at 0:26:88:38:c6:48 on en0 ifscope [ethernet]
? (192.168.50.255) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]
> **<enter key>**
? (192.168.50.1) at 0:26:88:38:c6:48 on en0 ifscope [ethernet]
? (192.168.50.255) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]
> **<enter key>**
**_Example Code:_** #!/usr/bin/env python
from cmd import Cmd
from time import ctime
import csv, os, subprocess, getpass, socket, pwd, re, select, shutil, subprocess, sys
syntaxError = "Sorry that syntax isn't quite right..."
class cliPrompt(Cmd):
def do_test(self, args):
if len(args) == 0:
print syntaxError
if args == '?':
print 'want to read the help?'
if args == 'arp':
subprocess.call('arp -an', shell=True)
if args == 'cpu':
subprocess.call('grep "model name" /proc/cpuinfo', shell=True)
if args == 'firewall':
subprocess.call('iptables -L -v -n --line-numbers', shell=True)
if args == 'interfaces':
subprocess.call('ifconfig', shell=True)
else:
pass
if __name__ == '__main__':
prompt = cliPrompt()
prompt.prompt = '>'
prompt.cmdloop()
Answer: Right on the front page of the cmd documentation discusses disabling the
returning previous command option.
<https://wiki.python.org/moin/CmdModule>
|
Internal Server Error with Flask app on Apache using Raspbian
Question: I can successfully deploy my flask app from the localhost:5000 but I get an
internal server error 500 when connecting through a web browser at
raspberrypi.local and the same error when I tried the RPi's IP
apache error log shows
Mon Jul 14 23:25:01 2014] [error] [client 192.168.1.118] mod_wsgi (pid=2081): Target WSGI script '/var/www/Intr
anet_for_RPi/Intranet_for_RPi.wsgi' cannot be loaded as Python module.
[Mon Jul 14 23:25:01 2014] [error] [client 192.168.1.118] mod_wsgi (pid=2081): Exception occurred processing WSG
I script '/var/www/Intranet_for_RPi/Intranet_for_RPi.wsgi'.
[Mon Jul 14 23:25:01 2014] [error] [client 192.168.1.118] Traceback (most recent call last):
[Mon Jul 14 23:25:01 2014] [error] [client 192.168.1.118] File "/var/www/Intranet_for_RPi/Intranet_for_RPi.wsg
i", line 7, in <module>
[Mon Jul 14 23:25:01 2014] [error] [client 192.168.1.118] from Intranet_for_RPi import app as application
[Mon Jul 14 23:25:01 2014] [error] [client 192.168.1.118] ImportError: No module named Intranet_for_RPi
/etc/apache2sites-available/
<VirtualHost *:80>
ServerName raspberrypi
ServerAdmin [email protected]
WSGIScriptAlias / /var/www/Intranet_for_RPi/Intranet_for_RPi.wsgi
<Directory /var/www/Intranet_for_RPi/Intranet_for_RPi/>
Order allow,deny
Allow from all
WSGIScriptReloading On
</Directory>
Alias /static /var/www/Intranet_for_RPi/Intranet_for_RPi/static
<Directory /var/www/Intranet_for_RPi/Intranet_for_RPi/static/>
Order allow,deny
Allow from all
</Directory>
ErrorLog ${APACHE_LOG_DIR}/error.log
LogLevel warn
CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>
flask file
# all the imports
from __future__ import with_statement
import sqlite3
import os
from contextlib import closing
from flask import Flask, request, session, g, redirect, url_for, \
abort, render_template, flash, send_from_directory
from werkzeug import secure_filename
# configuration
DATABASE = '/tmp/flaskr.db'
DEBUG = True
SECRET_KEY = 'key-gen secret'
USERNAME = 'admin'
PASSWORD = 'default'
app = Flask(__name__)
app.config.from_object(__name__)
app.config.from_envvar('FLASKR_SETTINGS', silent=True)
# This is the path to the upload directory
app.config['UPLOAD_FOLDER']='/var/www/Intranet_for_RPi/Intranet_for_RPi/uploads'
# These are the extensions that we are accepting to be uploaded
app.config['ALLOWED_EXTENSIONS'] = set(['txt', 'pdf', 'jpg', 'jpeg', 'gif'])
# For a given file, return whether it's an allowed type or not
def allowed_file(filename):
return '.' in filename and \
filename.rsplit('.', 1)[1] in app.config['ALLOWED_EXTENSIONS']
# This route will show a form to perform an AJAX request
# jQuery is loaded to execute the request and update the value of the operation
@app.route('/index')
def index():
return render_template('index.html')
# Route that will process the file upload
@app.route('/upload', methods=['POST'])
def upload():
# Get the name of the uploaded files
uploaded_files = request.files.getlist("file[]")
filenames = []
for file in uploaded_files:
# Check if the file is one of the allowed types/extensions
if file and allowed_file(file.filename):
#Make the filename safe, remove unsupported chars
filename = secure_filename(file.filename)
#Move teh file from the temporal folder to the upload folder we setup
file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
# Save teh filename into a list, we'll use it later
filenames.append(filename)
# Redirect the user to the uploaded_file route, which will basically
# show on the browser the uploaded file
# Load an html page with a link to each uploaded file
return render_template('upload.html', filenames=filenames)
# This route is expecting a parameter containing the name of a file. Then it will locate that
# file on the upload directory and show it on the browser, so if the user uploads an image,
# that image is going to be shown after the upload.
@app.route('/uploads/<filename>')
def uploaded_file(filename):
return send_from_directory(app.config['UPLOAD_FOLDER'], filename)
def connect_db():
return sqlite3.connect(app.config['DATABASE'])
def init_db():
with closing(connect_db()) as db:
with app.open_resource('schema.sql') as f:
db.cursor().executescript(f.read())
db.commit()
@app.before_request
def before_request():
g.db = connect_db()
@app.teardown_request
def teardown_request(exception):
g.db.close()
@app.route('/')
def show_entries():
cur = g.db.execute('select title, text from entries order by id desc')
entries = [dict(title=row[0], text=row[1]) for row in cur.fetchall()]
return render_template('show_entries.html', entries=entries)
@app.route('/add', methods=['POST'])
def add_entry():
if not session.get('logged_in'):
abort(401)
g.db.execute('insert into entries (title, text) values (?, ?)',
[request.form['title'], request.form['text']])
g.db.commit()
flash('New entry was successfully posted')
return redirect(url_for('show_entries'))
@app.route('/login', methods=['GET', 'POST'])
def login():
error = None
if request.method == 'POST':
if request.form['username'] != app.config['USERNAME']:
error = 'Invalid username'
elif request.form['password'] != app.config['PASSWORD']:
error = 'Invalid password'
else:
session['logged_in'] = True
flash('You were logged in')
return redirect(url_for('show_entries'))
return render_template('login.html', error=error)
@app.route('/logout')
def logout():
session.pop('logged_in', None)
flash('You were logged out')
return redirect(url_for('show_entries'))
@app.route('/files')
def files():
return render_template('files.html')
if __name__ == '__main__':
app.run()
Here is my wsgi file
#!/usr/bin/python
Import sys
import logging
logging.basicConfig(stream=sys.stderr)
sys.path.insert(0,"/var/www/Intranet_for_RPi/")
from Intranet_for_RPi import app as application
application.secret_key = 'key-gen-secret'
```
I have made the wsgi file executable. I think it may have something to do with
my python version or path pertaining to `/etc/apache2/mods-
available/wsgi.conf`.
Any help would greatly be appreciated
Answer: The error obviously says that the `wsgi` script can't find `Intranet_for_RPi`
module.
Check your paths. You might need to add `WSGIPythonPath` to your apache
configuration:
WSGIPythonPath /var/www/Intranet_for_RPi:/var/www/Intranet_for_RPi/packages:etc
<VirtualHost *:80>
...
|
Getting this error _csv.Error: sequence expected in Python
Question: I am trying to write a python script called header.py where I have a list of
headers which is:-
header = ['name', 'age', 'gender']
I am trying to append a header to it and write it in a csv file.
Here is my code snippet:-
import csv
header = ['name', 'age', 'gender']
updated_csv_writer = csv.writer(open("updatedQueryOutput.csv", "w"),delimiter = ',')
appendAdd = header.append("address")
updated_csv_writer.writerow(appendAdd)
But I am getting this error:-
_csv.Error: sequence expected
I don't know what is wrong with my code. Any help?Thanks
Answer: `append` mutates the list but doesn't return it, so you need to move the
header.append statement out onto its own. See this top-level example:
Python 2.7.5+ (default, Feb 27 2014, 19:37:08)
[GCC 4.8.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> a = [1,2,3]
>>> a.append(4)
>>> a
[1, 2, 3, 4]
So you could modify your code like this:
import csv
header = ['name', 'age', 'gender']
updated_csv_writer = csv.writer(open("updatedQueryOutput.csv", "w"),delimiter = ',')
header.append("address")
updated_csv_writer.writerow(header)
If you wanted to preserve the original value of `header`, you could always
make a new list like this:
header_new = header + ['address']
|
How to make selenium webdriver open in google chrome without Incognito
Question: I'm using selenium for the past 1 month. I want to create some small
applications using selenium. Selenium webdriver opens an incognito window when
I run it. Is there any way to make it launch in normal window(i.e which has my
accounts logged in)?
This is the code which I'm using : (python code in linux)
chromedriver = Path to chrome driver
os.environ["webdriver.chrome.driver"] = chromedriver
driver = webdriver.Chrome(chromedriver)
driver.get("http://www.gmail.com")
Answer: If you want to re-use your login/authentication cookies, you can save the
cookies and then load it again.
You can refer to [this post](http://stackoverflow.com/questions/15058462/how-
to-save-and-load-cookies-using-python-selenium-webdriver/15058521#15058521):
To save cookies:
import pickle
import selenium.webdriver
driver = selenium.webdriver.Firefox()
driver.get("http://www.google.com")
pickle.dump( driver.get_cookies() , open("cookies.pkl","wb"))
To add back the cookies:
import pickle
import selenium.webdriver
driver = selenium.webdriver.Firefox()
driver.get("http://www.google.com")
cookies = pickle.load(open("cookies.pkl", "rb"))
for cookie in cookies:
driver.add_cookie(cookie)
If you want to load an extension when Chrome starts, you can refer to [this
post](http://stackoverflow.com/questions/10425799/selenium-chromedriver-
causes-chrome-to-start-without-configured-plugins-bookmar/10434536#10434536)
and [this
post](https://sites.google.com/a/chromium.org/chromedriver/extensions).
|
Python, virtualenv: Getting permission error while activating
Question: I have been given a laptop. So I copied from my Work PC `.virtualenvs/`
directory to my NAS and then I copied it back to my new laptop.
I installed `virtualenv` and `virtualenvwrapper` but I can't get my virtual
environment to work. This is what I got at first:
chris@chris-amilo ~ $ workon iwidget
virtualenvwrapper.user_scripts could not run "/home/chris/.virtualenvs/preactivate": [Errno 13] Permission denied
virtualenvwrapper.user_scripts could not run "/home/chris/.virtualenvs/iwidget/bin/preactivate": [Errno 13] Permission denied
then I did a chmod +x to those files. Although I could change to this
environment after, no library can be seen.
I also get this:
chris@chris-amilo ~ $ ./.virtualenvs/iwidget/bin/activate
bash: ./.virtualenvs/iwidget/bin/activate: Permission denied
Also, the following shows that although I can `workon` on certain env, nothing
can be imported: (after I did a chmod +x to preactivate files)
chris@chris-amilo ~ $ workon iwidget
(iwidget)chris@chris-amilo ~ $ python
Python 2.7.6 (default, Mar 22 2014, 22:59:56)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pytz
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named pytz
>>>
(iwidget)chris@chris-amilo ~ $ ls .virtualenvs/iwidget/lib/python2.7/site-packages/py
py4j/ pytz/
py4j-0.8.1-py2.7.egg-info/ pytz-2014.2-py2.7.egg-info/
python_dateutil-2.2-py2.7.egg-info/
How can I fix this?
Answer: Moving virtualenvs is tricky. It's a much better bet to rebuild them from
scratch on the new machine. If you're using a requirements file, this is
trivial: just do `pip install -r requirements.txt`. If you're not using one,
create it on the old machine with `pip freeze > requirements.txt`.
|
Finding all maximal monotone subsequences in python
Question: Now trying to figure out how to find all the maximal subsequences(both
positive and negative) in sequence. Here I got some troubles, because there is
no suitable solution found. I've this code, but the output is ok only for
positive numbers. I'm newbie to python so can not figure out in short time how
can this be handled.
testcase = [1,2,3,4,5,4,3,2,1,0,-1,-2,-3,-2,-1,-2,-1,-2,-3,-4,-5]
def process(lst):
def sub(lst):
temp = []
while lst and (not temp or temp[-1] <= lst[0]):
temp.append(lst[0])
lst = lst[1:]
return temp, lst
res=[]
while lst:
subres, lst = sub(lst)
res.append(subres[0] if len(subres)==1 else subres)
return res
if __name__ == "__main__":
print(process(testcase))
So, the sample output is
[[1, 2, 3, 4, 5], 4, 3, 2, 1, 0, -1, -2, [-3, -2, -1], [-2, -1], -2, -3, -4, -5]]
While, I want it to be
[[1,2,3,4],[5,4,3,2,1,0,-1,-2,-3],[-2,-1],-2,[-1,-2,-3,-4,-5]]
So, the question is how can this be done?
Answer: You basically need to track the "derivative" (difference between elements),
and see when it changes direction.
You can express this very cleanly using `numpy`:
import numpy as np
np_split_indexes= np.where(np.diff(np.diff(testcase))!=0)[0]+2
split_indexes= [0] + list(np_split_indexes) + [len(testcase)]
result= [testcase[a:b] for a,b in zip(split_indexes[:-1],split_indexes[1:])]
or, if you prefer pure python:
result=[]
tmp=[]
last_direction=0;
last_element=0;
for x in testcase:
direction= (x-last_element)/abs(x-last_element) #math trick - divide by the magnitude to get the direction (-1/1)
last_element= x
if (direction!=last_direction) and tmp:
result.append(tmp)
tmp=[]
last_direction= direction
tmp.append(x)
if tmp:
result.append(tmp)
print result
output:
[[1, 2, 3, 4, 5], [4, 3, 2, 1, 0, -1, -2, -3], [-2, -1], [-2], [-1], [-2, -3, -4, -5]]
Note this differs from your intended output on the end. I'm not sure why you
grouped `-1` in the last group, since it's a local maximum.
|
numpy array equivalent for += operator
Question: I often do the following:
import numpy as np
def my_generator_fun():
yield x # some magically generated x
A = []
for x in my_generator_fun():
A += [x]
A = np.array(A)
Is there a better solution to this which operates on a numpy array from the
start and avoids the creation of a standard python list?
Note that the += operator allows to extend an empty and dimensionless array
with an arbitrarily dimensioned array whereas np.append and np.concatenate
demand for equally dimensioned arrays.
Answer: Use
[`np.fromiter`](http://docs.scipy.org/doc/numpy/reference/generated/numpy.fromiter.html):
def f(n):
for j in range(n):
yield j
>>> np.fromiter(f(5), dtype=np.intp)
array([0, 1, 2, 3, 4])
If you know beforehand the number of items the iterator is going to return,
you can speed things up using the `count` keyword argument:
>>> np.fromiter(f(5), dtype=np.intp, count=5)
array([0, 1, 2, 3, 4])
|
Inconsistent Execution Time in Python on all systems
Question: Something that's been driving me crazy with python... I used to think it was
[just Windows](http://stackoverflow.com/questions/24749808/), but I was wrong.
I can have the same exact code and run it multiple times and it executes in
wildly different amounts of time. Take the following test code, for example:
import math
def fib(count):
x = 0
while x < count:
a = int(((((1 + math.sqrt(5)) / 2) ** x) - (((1 - math.sqrt(5)) / 2) ** (x))) / math.sqrt(5))
x+=1
if __name__ == '__main__':
import timeit
t = timeit.Timer("fib(1250)", setup="from __main__ import fib",)
#print t.timeit(10)
count = 10000
results = t.repeat(count, 1)
min = 0xFFFF
max = 0
sum = 0
for i in results:
i = i*1000.0
if i < min: min = i
if i > max: max = i
sum+=i
print "Min {:.3f} | Max {:.3f} | Max/Min {:.3f} | Avg {:.3f}".format(min, max, max/min, sum/count)
Basically, it generates the first 1250 elements of fibonacii 10,000 times and
uses timeit to get the amount of time each run takes. I then coalesce those
times and find min, max, average and variance between min and max (the spread,
if you will).
Here's the results:
Windows: Min 3.071 | Max 8.903 | Max/Min 2.899 | Avg 3.228
Mac OS: Min 1.531 | Max 3.167 | Max/Min 2.068 | Avg 1.621
Ubuntu: Min 1.242 | Max 10.090 | Max/Min 8.123 | Avg 1.349
So, Linux is the fastest but also has the most variance. By a LOT. But all of
them can have a pretty wild swing: Only 200% for Mac, but 290% for Windows and
810% for linux!
Is it actually taking that much different time to execute? Is timeit not
accurate enough? Is there something else I am missing? I'm working a lot with
generating animations and I need as consistent time as possible.
Answer: You are measuring very short times, and then even a little bit of something
happening somewhere has a big impact.
I ran your test script on my machine (OS X, Core i7, Python 2.7) and made this
plot of `results`:
You can see that most of the time the timing results are very consistent, but
there are isolated incidents of the algorithm taking much more time (because
there is something else happening).
* * *
I made a tiny adjustment to your timing procedure:
results=t.repeat(10, 1000)
So, now we are timing runs of 1000 function calls. The total amount of time is
the same, naturally (10000 calls):
Now you can see that the performance is much more predictable. It may be that
part of your wobbly timings are due to the timing methodology, not due really
different times to carry out anything. Millisecond-level timing is difficult
in a real-world OS environment. Even when your computer is "doing nothing", it
is still switching tasks, doing background jobs, etc.
* * *
I understand the original point was not to calculate the Fibonacci numbers.
But if it were, then choosing the right tool makes a difference:
import numpy as np
def fib(count):
x = np.arange(count)
a = (((1 + np.sqrt(5))/2) ** x - ((1 - np.sqrt(5)) / 2) ** x) / np.sqrt(5)
a = a.astype('int')
This gives:
Min 0.120 | Max 0.471 | Max/Min 3.928 | Avg 0.125
Ten-fold speed improvement.
* * *
About the images in this answer, they are plotted with `matplotlib`. The first
one is done thus:
import matplotlib.pyplot as plt
# create a figure
fig = plt.figure()
# create axes into the figure
ax = fig.add_subplot(111)
# plot the vector results with dots of size 2 (points) and semi-transparent blue color
ax.plot(results, '.', c=(0, 0, 1, .5), markersize=2)
See the documentation of `matplotlib`. It is easiest to get started by using
`IPython` and `pylab`.
|
Trying to load JSON into d3 treemap without using a GET
Question: I am using <http://bost.ocks.org/mike/treemap/> to attempt to incorporate a D3
treemap into Splunk. However, it errors on the d3.JSON("flare.json") as it
can't find the file. I have tried putting the JSON array right into the js and
calling root = JSON.parse(myjson), but then then it arrays with unexpected
character JSON.parse. If you look at the js from Bostick's page, you can see
that I can't just remove the d3.JSON, because it calls back to the functions
that actually render the treemap.
Do you have any ideas on how I can fix this?
renderResults: function($super, results) {
if(!results) {
this.resultsContainer.html('No content available.');
return;
}
var margin = {top: 20, right: 0, bottom: 0, left: 0},
width = 960,
height = 500 - margin.top - margin.bottom,
formatNumber = d3.format(",d"),
transitioning;
var x = d3.scale.linear()
.domain([0, width])
.range([0, width]);
var y = d3.scale.linear()
.domain([0, height])
.range([0, height]);
var treemap = d3.layout.treemap()
.children(function(d, depth) { return depth ? null : d._children; })
.sort(function(a, b) { return a.value - b.value; })
.ratio(height / width * 0.5 * (1 + Math.sqrt(5)))
.round(false);
var svg = d3.select("#chart").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.bottom + margin.top)
.style("margin-left", -margin.left + "px")
.style("margin.right", -margin.right + "px")
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")")
.style("shape-rendering", "crispEdges");
var grandparent = svg.append("g")
.attr("class", "grandparent");
grandparent.append("rect")
.attr("y", -margin.top)
.attr("width", width)
.attr("height", margin.top);
grandparent.append("text")
.attr("x", 6)
.attr("y", 6 - margin.top)
.attr("dy", ".75em");
var myjson = not including the actual array to save space
root = JSON.parse(myjson);
d3.json("flare.json", function(root) {
initialize(root);
accumulate(root);
layout(root);
display(root);
function initialize(root) {
root.x = root.y = 0;
root.dx = width;
root.dy = height;
root.depth = 0;
}
// Aggregate the values for internal nodes. This is normally done by the
// treemap layout, but not here because of our custom implementation.
// We also take a snapshot of the original children (_children) to avoid
// the children being overwritten when when layout is computed.
function accumulate(d) {
return (d._children = d.children)
? d.value = d.children.reduce(function(p, v) { return p + accumulate(v); }, 0)
: d.value;
}
// Compute the treemap layout recursively such that each group of siblings
// uses the same size (1×1) rather than the dimensions of the parent cell.
// This optimizes the layout for the current zoom state. Note that a wrapper
// object is created for the parent node for each group of siblings so that
// the parent’s dimensions are not discarded as we recurse. Since each group
// of sibling was laid out in 1×1, we must rescale to fit using absolute
// coordinates. This lets us use a viewport to zoom.
function layout(d) {
if (d._children) {
treemap.nodes({_children: d._children});
d._children.forEach(function(c) {
c.x = d.x + c.x * d.dx;
c.y = d.y + c.y * d.dy;
c.dx *= d.dx;
c.dy *= d.dy;
c.parent = d;
layout(c);
});
}
}
function display(d) {
grandparent
.datum(d.parent)
.on("click", transition)
.select("text")
.text(name(d));
var g1 = svg.insert("g", ".grandparent")
.datum(d)
.attr("class", "depth");
var g = g1.selectAll("g")
.data(d._children)
.enter().append("g");
g.filter(function(d) { return d._children; })
.classed("children", true)
.on("click", transition);
g.selectAll(".child")
.data(function(d) { return d._children || [d]; })
.enter().append("rect")
.attr("class", "child")
.call(rect);
g.append("rect")
.attr("class", "parent")
.call(rect)
.append("title")
.text(function(d) { return formatNumber(d.value); });
g.append("text")
.attr("dy", ".75em")
.text(function(d) { return d.name; })
.call(text);
function transition(d) {
if (transitioning || !d) return;
transitioning = true;
var g2 = display(d),
t1 = g1.transition().duration(750),
t2 = g2.transition().duration(750);
// Update the domain only after entering new elements.
x.domain([d.x, d.x + d.dx]);
y.domain([d.y, d.y + d.dy]);
// Enable anti-aliasing during the transition.
svg.style("shape-rendering", null);
// Draw child nodes on top of parent nodes.
svg.selectAll(".depth").sort(function(a, b) { return a.depth - b.depth; });
// Fade-in entering text.
g2.selectAll("text").style("fill-opacity", 0);
// Transition to the new view.
t1.selectAll("text").call(text).style("fill-opacity", 0);
t2.selectAll("text").call(text).style("fill-opacity", 1);
t1.selectAll("rect").call(rect);
t2.selectAll("rect").call(rect);
// Remove the old node when the transition is finished.
t1.remove().each("end", function() {
svg.style("shape-rendering", "crispEdges");
transitioning = false;
});
}
return g;
}
function text(text) {
text.attr("x", function(d) { return x(d.x) + 6; })
.attr("y", function(d) { return y(d.y) + 6; });
}
function rect(rect) {
rect.attr("x", function(d) { return x(d.x); })
.attr("y", function(d) { return y(d.y); })
.attr("width", function(d) { return x(d.x + d.dx) - x(d.x); })
.attr("height", function(d) { return y(d.y + d.dy) - y(d.y); });
}
function name(d) {
return d.parent
? name(d.parent) + "." + d.name
: d.name;
}
};
}
I am still not 100% sure how these two even are able to interact. I have a
little JavaScript experience, but no Python experience. The way Splunk
integrates all these scripts together is baffling.
import cherrypy
import controllers.module as module
import splunk, splunk.search, splunk.util, splunk.entity
import json
from splunk.appserver.mrsparkle.lib import jsonresponse
import lib.util as util
import lib.i18n as i18n
import logging
logger = logging.getLogger('splunk.module.TreeMap1')
import math
import cgi
class TreeMap1(module.ModuleHandler):
def generateResults(self, host_app, client_app, sid, count=1000,
offset=0, entity_name='results'):
count = max(int(count), 0)
offset = max(int(offset), 0)
if not sid:
raise Exception('TreeMap1.generateResults - sid not passed!')
try:
job = splunk.search.getJob(sid)
except splunk.ResourceNotFound, e:
logger.error('TreeMap could not find job %s. Exception: %s' % (sid, e))
return _('<p class="resultStatusMessage">Could not get search data.</p>')
dataset = getattr(job, entity_name)[offset: offset+count]
outputJSON = {}
for i, result in enumerate(dataset):
tdict = {}
tdict[str(result.get('itemName', None))] = str(result.get('totalCPU', None))
name = str(result.get('itemCat', None))
if name not in outputJSON:
outputJSON[name] = dict()
outputJSON[name].update(tdict)
cherrypy.response.headers['Content-Type'] = 'text/json'
return json.dumps(outputJSON, sort_keys=True)
def render_json(self, response_data, set_mime='text/json'):
cherrypy.response.headers['Content-Type'] = set_mime
if isinstance(response_data, jsonresponse.JsonResponse):
response = response_data.toJson().replace("</", "<\\/")
else:
response = json.dumps(response_data).replace("</", "<\\/")
return ' ' * 256 + '\n' + response
Answer: D3's `d3.JSON(url, ...)` literally performs a GET request and attempts to
parse the response as JSON*; it is similar to jQuery's `$.getJSON(url, ...)`.
If you already have the JSON necessary to construct the tree map, just ignore
the call altogether and go straight to the callback. **If you already have an
array/object, you don't need`JSON.parse`**; JSON.parse turns a valid JSON
string into an array/object.
*See the documentation on [d3.json](https://github.com/mbostock/d3/wiki/Requests) for more...
Along the same lines, if you already have the data, you can just use:
...
var myJSON = [ ... ] //The actual array you're loading.
initialize(myJSON);
accumulate(myJSON);
layout(myJSON);
display(myJSON);
...
**However,** notice what you're actually doing in the code above. You're
passing an _array_ into `initialize` \-- which appears to want an _object_ :
function initialize(root) { //Root in this case is myVar -- an ARRAY.
root.x = root.y = 0; //Arrays don't have fields. This is BAD.
root.dx = width;
root.dy = height;
root.depth = 0;
}
Thus, what you should do is figure out what type of structure `myJSON` should
use.
* * *
If the error that you want to fix is actually that the "flare.json" file can't
be found, then your problem is actually _server-side_. How are you serving the
flare.json file? Try accessing it in your browser to make sure it is located
where you think it is.
|
Hashlib md5 in python returning incorrect digests for some unicode characters?
Question: I have been playing around with python's and Java's MD5 implementation and
encountered this quirk that's been puzzling me.
The following python script illustrates the problem:
# -*- coding: utf-8 -*-
import hashlib
def md5hash(x):
m = hashlib.md5()
m.update(x)
return m.hexdigest()
print md5hash('\xdb')
print md5hash('Û')
Output:
98fd00d788afe2a5fa5e4f8e1666638b
31ecfb09f120720a55d96a2034f5d00b
I expected the two digests to be equivalent, given that `Û` ought to be
equivalent to `\xdb`. I built an equivalent implementation in Java to get some
more insight:
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class Test {
public static void main(String[] args) throws Exception {
MessageDigest m = MessageDigest.getInstance("MD5");
m.update("\u00db".getBytes());
System.out.println(bytesToHex(m.digest()));
m.update("Û".getBytes());
System.out.println(bytesToHex(m.digest()));
}
final protected static char[] hexArray = "0123456789abcdef".toCharArray();
public static String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for ( int j = 0; j < bytes.length; j++ ) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
}
Output:
31ecfb09f120720a55d96a2034f5d00b
31ecfb09f120720a55d96a2034f5d00b
The output of Java is consistent, as expected. This is leading me to believe
that `md5hash('\xdb')` is outputting an incorrect result, but I am not sure
what it is that I'm missing. Any thoughts?
Answer: Your assumptions are incorrect. You started your Python source code with:
# -*- coding: utf-8 -*-
`Û` is **not** equivalent to `\xdb` in that case; it is instead two bytes:
>>> u'Û'.encode('utf8')
'\xc3\x9b'
Python is entirely consistent here:
>>> import hashlib
>>> hashlib.md5('\xc3\x9b').hexdigest()
'31ecfb09f120720a55d96a2034f5d00b'
>>> hashlib.md5('\xdb').hexdigest()
'98fd00d788afe2a5fa5e4f8e1666638b'
In Java you started with a Unicode codepoint instead, converting that to UTF-8
bytes:
"\u00db".getBytes()
The Python equivalent would be to use a `unicode` string literal and either a
`\uhhhh` or `\xhh` escape sequence:
>>> u'\u00db'.encode('utf8')
'\xc3\x9b'
>>> u'\xdb'.encode('utf8')
'\xc3\x9b'
Note the `u` prefix to produce a `unicode` string. `\xdb` without a `u` prefix
is a _byte string_ , not a Unicode codepoint, and only if you were to decode
it as _Latin 1_ would you get the same Unicode string:
>>> '\xdb'.decode('latin1')
u'\xdb'
>>> '\xdb'.decode('latin1').encode('utf8')
'\xc3\x9b'
You probably want to study up on Python and Unicode; see:
* The [Python Unicode HOWTO](http://docs.python.org/2/howto/unicode.html)
* [Pragmatic Unicode](http://nedbatchelder.com/text/unipain.html) by Ned Batchelder
and for completeness sake:
* [The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)](http://joelonsoftware.com/articles/Unicode.html) by Joel Spolsky
|
How to collect the value corresponding to a field of an array/list of named tuples
Question: I am new to Python, in the process of migrating from MATLAB. I was using the
`namedtuple` class the following way.
from collections import namedtuple
import numpy as np
MyStruct = namedtuple("MyStruct", "field1 field2 field3")
d = []
d.append(MyStruct(field1=np.array(3,'int'),field2=np.array(4,'int'),field3=np.array(5,'int')))
d
d.append(MyStruct(field1=np.array(4,'int'),field2=np.array(5,'int'),field3=np.array(6,'int')))
Here `d` is a 2-element list of `namedtuple` objects. What I want is to obtain
an array of all `field1` values through all the elements of `d` in a nifty way
without the need to iterate through the elements of `d`. Something similar to
MATLAB, where we put square brackets around an array of structures.
I'd appreciate any insights into this matter.
Srini
Answer: This is what list comprehensions are for:
field1vals = [x.field1 for x in d]
|
Python Dict from CSV IndexError
Question: I need to compare 2 CSV files and I am trying to use the @Martijn Pieters
solution at [Python: Comparing two CSV files and searching for similar
items](http://stackoverflow.com/questions/5268929/python-comparing-two-csv-
files-and-searching-for-similar-items) but I am running into an error:
IndexError: list index out of range
Here is the code I am using,
import csv
with open('filename.csv', 'rb') as a:
indices = dict((r[2], i) for i, r in enumerate(csv.reader(a)))
print indices
filename.csv has 10 columns and 2000 rows. I want to index column 3 that has
hostnames and then match with hostnames in other .csv file
type,id,hostname,os,,,,
phy,123,server1,rhel5,,,,
vir,234,server2,rhel6,,,,
I am not sure why I am getting IndexError. Please help to fix the problem.
Answer: You probably have empty lines at the start or end of your csv file.
I was able to reproduce this error with the following code:
import csv
with open('filename.csv', 'wb') as a:
strng = """
type,id,hostname,os,,,,
phy,123,server1,rhel5,,,,
vir,234,server2,rhel6,,,,
"""
a.write(strng)
with open('filename.csv', 'rb') as a:
indices = dict((r[2], i) for i, r in enumerate(csv.reader(a)))
print indices
However when I removed those blank lines, the code runs perfectly :
import csv
with open('filename.csv', 'wb') as a:
strng = """type,id,hostname,os,,,,
phy,123,server1,rhel5,,,,
vir,234,server2,rhel6,,,,
"""
a.write(strng)
with open('filename.csv', 'rb') as a:
indices = dict((r[2], i) for i, r in enumerate(csv.reader(a)))
print indices
Refer to this [SO Answer](http://stackoverflow.com/a/18891114/3244627) on how
to skip blank lines in csv.
|
progressbar in Tkinter with a label inside
Question: Is It possible to improve my progressbar in Tkinter-Python adding a label in
the middle (ex: reading file)?
I tried to find a elegant coding solution but without a real result
from Tkinter import *
import ttk
import tkFileDialog
import time
class MainWindow(Frame):
def __init__(self):
Frame.__init__(self)
self.master.title("ProgressBar example")
self.master.minsize(200, 100)
self.grid(sticky=E+W+N+S)
top = self.winfo_toplevel()
top.rowconfigure(0, weight=1)
top.columnconfigure(0, weight=1)
self.start_ind = Button(self, text='Start indeterminate', command=self.start_ind, activeforeground="red")
self.start_ind.grid(row=0, column=0, pady=2, padx=2, sticky=E+W+N+S)
self.pbar_ind = ttk.Progressbar(self, orient="horizontal", length=300, mode="indeterminate")
self.pbar_ind.grid(row=1, column=0, pady=2, padx=2, sticky=E+W+N+S)
def start_ind(self):
for i in xrange(50):
self.pbar_ind.step(1)
self.update()
# Busy-wait
time.sleep(0.1)
if __name__=="__main__":
d = MainWindow()
d.mainloop()
Answer: Have you tried creating a text Label and putting it in the same row/column and
setting it the same size like so:
self.Lab = Label(self,length=200)
self.Lab.grid(row=1,column=0,pady=2,padx=2,sticky=E+W+N+S))
But you would want to put it after the progress bar widget.
|
Is there a built-in Django template filter that finds the first value in a list to satisfy a condition?
Question: In a Django template, how do I return the first element of a list that matches
a condition? The list could be empty. I want to know if there is a filter that
finds the first element in an iterable to match a particular condition, then
stops checking, similar to Python's
[next](https://docs.python.org/2/library/functions.html#next)
(<http://stackoverflow.com/a/2364277/1337422>).
>>> lis = ['a', 1, 40, 'three', 5]
>>> next(x for x in lis if x == 1)
1
Answer: There isn't a built in Django template filter that does this.
If it is a particular condition you want to match, then it would be easy to
write a [custom template
filter](https://docs.djangoproject.com/en/dev/howto/custom-template-
tags/#writing-custom-template-filters). For example:
from django import template
register = template.Library()
@register
def first_one_in_list(l):
return next((x for x in l if x==1), default=None) # specify default to avoid stop iteration
If you want to specify an arbitrary condition in the template, I think you'd
need to do something hacky. The Django template language is designed to
prevent complex logic in templates.
|
Importing modules Python
Question: Hey I am having some trouble figuring out what is being asked to import in
this code
#!/opt/local/bin/python
import sys
from formatter import Formatter
def main():
#do stuff
in my class formatter.py, do I have had to define a function with a name
Formatter. A little confused on this. I have been testing my code by putting
from formatter import *
Which takes all the definitions in my class(I believe).
Answer: your line `from formatter import Formatter` will search through the module
formatter for anything with the name `Formatter`. so if you had a function
called `Formatter` in that module, it would be imported, meaning you could use
it in your main section (anywhere below the import line will work) It will
import classes as well.
`formatter.py` is a module. a class might look something like:
class A:
variable = 1
def b():
#do stuff
|
Syntax error with wexpect
Question: I did download the latest copy of `wexpect` from github and placed it in the
site-packages folder of my working directory for python. I also installed the
py32 packages as instructed. When I try to run the `import wexpect` command
from IDLE I get the following error message
import wexpect
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Python34\lib\site-packages\wexpect.py", line 94
except ImportError, e:
^
SyntaxError: invalid syntax
Could you please give me some pointers as to how to debug.
Answer: You're running the app using Python 3, while the syntax `except ImportError,
e:` is for Python 2. In Python 3, it's `except ImportError as e:`.
If it's a library code, either search for the latest version of the library
for Python 3, or run it using Python 2 otherwise.
|
Image searching system using Bag Of Features method
Question: I am doing a project making visual search system using Bag Of Features method
but have little question. If I understood the method correctly, the method has
few steps.
1. Feature extraction from an image
2. Vector quantization
3. Image searching from a database
I am stock at between 2 and 3. I use python package called scikit-learn to
quantize the feature vectors extracted using SIFT algorithm in opencv. For
now, I set the cluster size 8 with default setting. I tried to generate
histogram out of the output codebook and display it. I tried this with same
image several times but all the histograms looked different. The code is
below. It is a simple code.
import cv2
import numpy as np
import matplotlib.pyplot as plt
from sklearn.cluster import KMeans
def feature_extract(img):
sift = cv2.SIFT()
gray = img
kp, des = sift.detectAndCompute(gray, None)
return kp, des
def codebook(k, des):
km = KMeans(n_clusters=k, max_iter=500)
km.fit(des)
codebook = km.cluster_centers_
label = km.labels_
return codebook, label
img = cv2.imread('sift_example.jpg', 0)
kp, des = feature_extract(img)
k = 8
codebook, label = codebook(k, des)
plt.hist(label, bins=range(0,9), align='left'), plt.show()
I suspect that the problem come from the clustering error. Since the initial
centers for clustering is set to random, the final converged centers are
different. Is there any solution to this?
Answer: You are right about the randomness of KMeans initial centers, but I would
assume that if you dont explicitely change the initial seed of the random
number generator, then it would always pick the same "random" features as
initial centers. Another reason could be that, if feature detection/extraction
is multithreaded, the features computed on your image can appear in different
orders between each run. You might check that aswell.
Alternatively, you can pass your own centers to KMeans as initial centroids so
you could pick them or generate them by yourself to make sure KMeans starts
with always the same initial centers
|
Python: "import JSON... json.loads(request.body)" 2.7->3.4
Question: I recently converted a django server to python version 3.4.1 from python
version 2.7. My request.body is an array serialized to JSON. When de-
serialized it will be a python list.
Unfortunately, it would seem that json.loads no longer takes raw bytes (which
is what request.body is).
How can I fix this issue?
def index(request):
if request.method == 'POST':
print("Made it here!")
registered = []
notRegistered = []
print("Is it this?")
print(repr(request.body))
data = json.loads(request.body)
print("Did I make it here?")
The last call to print never executes, which is why I'm assuming it has to do
with json.loads()
Answer: I would expect a traceback to occur rather than just "the last line never
executing", but that aside...
# Let's just assume the request is UTF-8 encoded.
data = json.loads(request.body.decode('utf-8'))
|
How to assign a value to a radiobutton in pyqt?
Question: I want to assign a value to a radiobutton when it is checked.
def radiobutton8(self):
if self.radioButton_8.isChecked():
self.radioButton_8 = 02
However, this cannot work. Any solution?
UPDATE: My code has been edited to be:
class MyRadioButton(QtGui.QRadioButton):
def __init__(self):
super(MyRadioButton, self).__init__()
self.value = None
def SetValue(self, val):
self.value = val
def GetValue(self):
return self.value
class UserTool(QtGui.QDialog):
def setup(self, Dialog):
...
self.radioButton_8.toggled.connect(self.radiobutton8)
def retranslateUi(self, Dialog):
...
self.radioButton_8 = MyRadioButton()
self.radioButton_8.setText(_translate("Dialog", "A1", None))
def radiobutton8(self):
if self.radioButton_8.isChecked():
value = self.radioButton_8.setValue("02")
self.lcdNumber.display(value)
However, my original text 'A1' for the radio button is now missing and my
number still does not appear on my lcd when checked. Any idea why?
UPDATE: I edited my code to be something like that:
class MyRadioButton(QtGui.QRadioButton):
def __init__(self):
super(MyRadioButton, self).__init__()
self.value = None
def SetValue(self, val):
self.value = val
def GetValue(self):
return self.value
class UserTool(QtGui.QDialog):
def setup(self, Dialog):
...
self.lcdNumber = QtGui.QLCDNumber(Dialog)
self.lcdNumber.setGeometry(QtCore.QRect(590, 10, 71, 23))
self.lcdNumber.setFrameShadow(QtGui.QFrame.Raised)
self.lcdNumber.setObjectName(_fromUtf8("lcdNumber"))
self.lcdNumber.setStyleSheet("* {background-color: black; color: white;}")
self.lcdNumber.display('00')
self.radioButton_8 = QtGui.QRadioButton(Dialog)
self.radioButton_8.setGeometry(QtCore.QRect(460, 10, 82, 17))
self.radioButton_8.setChecked(False)
self.radioButton_8.setAutoExclusive(False)
self.radioButton_8.setObjectName(_fromUtf8("radioButton_8"))
self.radioButton_8 = MyRadioButton()
self.radioButton_8.setText("A1")
self.radioButton_8.setValue(02)
self.radioButton_8.toggled.connect(self.showValueFromRadioButtonToLCDNumber)
def showValueFromRadioButtonToLCDNumber(self):
value = self.radioButton_8.GetValue()
if self.radioButton_8.isChecked():
self.lcdNumber.display(value)
And then now I have this error:
Traceback (most recent call last):
File "C:/Users/Vivien Phua/Documents/Python Scripts/Rs232.py", line 303, in handleOpenWidget
self.popup = UserTool()
File "C:/Users/Vivien Phua/Documents/Python Scripts/Rs232.py", line 39, in __init__
self.setup(self)
File "C:/Users/Vivien Phua/Documents/Python Scripts/Rs232.py", line 153, in setup
self.radioButton_8.setValue(02)
AttributeError: 'MyRadioButton' object has no attribute 'setValue'
I have also tried the code you have given me and there is no such error, but
the LCD in your code does not show the value 02.
Answer: Do you mean text value next to radioButton? if so, here is solution:
def radiobutton8(self):
if self.radioButton_8.isChecked():
self.radioButton_8.setText("02")
**EDIT1** : radioButton doesn't have value field as you need. However, you can
write your own radiobButton class that inherits original QRadioButton, and add
that field. Example:
class MyRadioButton(QtGui.QRadioButton):
def __init__(self):
super(MyRadioButton, self).__init__()
self.value = None
def SetValue(self, val):
self.value = val
def GetValue(self):
return self.value
and use it like this:
self.radioButton_8 = MyRadioButton()
self.radioButton_8.setText("some text")
...
def radiobutton8(self):
if self.radioButton_8.isChecked():
self.radioButton_8.SetValue("02")# or .SetValue(2) if you want it to be integer
**EDIT2**
# -*- coding: utf-8 -*-
import sys
from PyQt4 import QtCore, QtGui
from PyQt4.QtCore import Qt
class MyRadioButton(QtGui.QRadioButton):
def __init__(self):
super(MyRadioButton, self).__init__()
self.value = None
def SetValue(self, val):
self.value = val
def GetValue(self):
return self.value
class Widget(QtGui.QWidget):
def __init__(self):
super(Widget, self).__init__()
self.layout = QtGui.QVBoxLayout(self)
self.pushButton_7 = QtGui.QPushButton("if RB is checked, show it's value to LCD")
self.pushButton_7.setGeometry(QtCore.QRect(220, 650, 75, 23))
self.pushButton_7.clicked.connect(self.showValueFromRadioButtonToLCDNumber)
self.radioButton = MyRadioButton()
self.radioButton.setText("some text")
self.radioButton.SetValue("02")# somewhere in code first set value to radio button
self.lcdNumber = QtGui.QLCDNumber()
self.layout.addWidget(self.pushButton_7)
self.layout.addWidget(self.radioButton)
self.layout.addWidget(self.lcdNumber)
def showValueFromRadioButtonToLCDNumber(self):
value = self.radioButton.GetValue()
if self.radioButton.isChecked():
self.lcdNumber.display(value)
if __name__ == '__main__':
app = QtGui.QApplication([])
w = Widget()
w.show()
sys.exit(app.exec_())
|
POST to .jsp website with Python requests library
Question: I'm using Python 3.3 and Requests 2.2.1.
I'm trying to POST to a website ending in .jsp, which then changes to .doh
ending. Using the same basic requests code outline I'm able to successfully
login and scrape other websites, but the javascript part on this site is not
working. This is my code:
import requests
url = 'https://prodpci.etimspayments.com/pbw/include/sanfrancisco/input.jsp'
payload = {'plateNumber':'notshown', 'statePlate':'CA'} #tried CA and California
s = requests.Session() #Tried 'session' and 'Session' following different advice
post = s.post(url, data=payload)
r = s.get('https://prodpci.etimspayments.com/pbw/include/sanfrancisco/input.jsp')
print(r.text)
Finally, when manually entering data into the webpage through firefox browser,
the page changes and url becomes
<https://prodpci.etimspayments.com/pbw/inputAction.doh>, which only has contet
if you are redirected there after typing in license plate.
From the printed text, I know I'm getting content from the page as it would be
without POSTing anything, but I need the content for the page once I've POSTed
the payload. For the POST payload, do I need to include something like
'submit':'submit' to simulate clicking the search button?
Am I doing the GET request from the right url, considering the url I POST to?
Answer: You're making POST request and after that another GET request and this is why
you get the same page with the form.
response = s.post(url, data=payload)
print(response.text)
Also if you check the form markup, you'll find its action is
`/pbw/inputAction.doh` and additionally the form sends a few parameters from
`hidden` inputs. Therefore you should use that URL in your request and
probably the values from `hidden` inputs.
With the next code I'm able to retrieve the same response as via regular
request in browser:
import requests
url = 'https://prodpci.etimspayments.com/pbw/inputAction.doh'
payload = {
'plateNumber': 'notshown',
'statePlate': 'CA',
'requestType': 'submit',
'clientcode': 19,
'requestCount': 1,
'clientAccount': 5,
}
s = requests.Session()
response = s.post(url, data=payload)
print(response.text)
The same you can see in browser after same request via the form:
...
<td colspan="2"> <li class="error">Plate is not found</li></td>
...
|
Why can't I catch SIGINT when asyncio event loop is running?
Question: Using Python 3.4.1 on Windows, I've found that while executing an [asyncio
event loop](https://docs.python.org/3/library/asyncio.html), my program can't
be interrupted (i.e. by pressing Ctrl+C in the terminal). More to the point,
the SIGINT signal is ignored. Conversely, I've determined that SIGINT is
handled when not in an event loop.
Why is it that SIGINT is ignored when executing an asyncio event loop?
The below program should demonstrate the problem - run it in the terminal and
try to stop it by pressing Ctrl+C, it should keep running:
import asyncio
import signal
# Never gets called after entering event loop
def handler(*args):
print('Signaled')
signal.signal(signal.SIGINT, handler)
print('Event loop starting')
loop = asyncio.SelectorEventLoop()
asyncio.set_event_loop(loop)
loop.run_forever()
print('Event loop ended')
See [discussion](https://groups.google.com/forum/#!topic/python-
tulip/pr9fgX8Vh-A) on official (Tulip) mailing list.
Answer: I've found a workaround, which is to schedule a periodic callback. While this
running, SIGINT is apparently processed:
import asyncio
def wakeup():
# Call again
loop.call_later(0.1, wakeup)
print('Event loop starting')
loop = asyncio.SelectorEventLoop()
# Register periodic callback
loop.call_later(0.1, wakeup)
asyncio.set_event_loop(loop)
loop.run_forever()
print('Event loop ended')
Not sure why this is necessary, but it indicates that signals are blocked
while the event loop waits for events ("polls").
The matter has been
[discussed](https://groups.google.com/forum/#!topic/python-tulip/pr9fgX8Vh-A)
on the official (Tulip) mailing list, my workaround is apparently the way to
go as of now.
## Update
A fix has supposedly [made its way into Python
3.5](https://code.google.com/p/tulip/issues/detail?id=191), so hopefully my
workaround will be made obsolete by that Python version.
|
Copy IPython's pretty printing of results
Question: When displaying results in [IPython](https://github.com/ipython) (without
using `print()`), nested objects gets an easy-to-view formatting. Is there a
way to create/copy a function in Python with the same pretty formatting
functionalities as IPython uses? I have been trying to look through their code
for a possible module to import, but it seems like an impossible task. Would
it be possible to write one yourself?
IPython example:
In [1]: {'Mario': {'Stats': [63, 10, 69, 24, 82], 'Result': [(2, 7, 5, {'ids':
[46737432927499418861568L, 61421050754327147184128L, 46239274047769245908992L]})]},
'Luigi': {'Results': [(7, 9, 6, {'ids': [20471482889415933558784L,
87284089722223609249792L, 27117156251036496691200L]})], 'Stats': [14, 71, 93, 49, 53]}}
Out[1]:
{'Luigi': {'Results': [(7,
9,
6,
{'ids': [20471482889415933558784L,
87284089722223609249792L,
27117156251036496691200L]})],
'Stats': [14, 71, 93, 49, 53]},
'Mario': {'Result': [(2,
7,
5,
{'ids': [46737432927499418861568L,
61421050754327147184128L,
46239274047769245908992L]})],
'Stats': [63, 10, 69, 24, 82]}}
**[EDIT]** I know of the `pprint` module, but it does not do indentations the
same way as IPython does (I don't want the indentation level of child elements
to be dependent on their parent).
What `pprint` outputs:
{'Luigi': {'Results': [(7,
9,
6,
{'ids': [20471482889415933558784L,
87284089722223609249792L,
27117156251036496691200L]})],
'Stats': [14, 71, 93, 49, 53]},
'Mario': {'Result': [(2,
7,
5,
{'ids': [46737432927499418861568L,
61421050754327147184128L,
46239274047769245908992L]})],
'Stats': [63, 10, 69, 24, 82]}}
Answer: Try the [pprint](https://docs.python.org/3/library/pprint.html) module.
Usually simply using `from pprint import pprint` and then using `pprint()`
instead of `print()` can get you decent results; its output can be customized
as well if you read over the module docs.
|
Running shell command in python and reading output
Question: I have the following:
cmd = "ps aux | grep 'java -jar' | grep -v grep | awk '//{print $2}'".split(' ')
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = p.communicate()
print out
When I run the command in the console (outside of python), I get the desired
output. Running this above code in python prints a blank line. I am assuming
there is something up with the `cmd` (specifically the `|` operator) but I
can't be sure.
I need to achieve this with the standard Python 2.6.6 install (no additional
modules)
Answer: You need to use a single call to `Popen()` for each piece of the original
command, as connected by the pipe, as in
import subprocess
p1 = subprocess.Popen(["ps", "aux"], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
p2 = subprocess.Popen(["grep", "java -jar"], stdin=p1.stdout, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
p3 = subprocess.Popen(["grep", "-v", "grep"], stdin=p2.stdout, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
p4 = subprocess.Popen(["awk", "//{print $2}"], stdin=p3.stdout, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = p4.communicate()
print out
The [subprocess
documentation](https://docs.python.org/2/library/subprocess.html#replacing-
shell-pipeline) has an in-depth discussion.
|
python run redis error when crontab shell
Question: i install redis-2.7.1 in my folder,and run my python code,it worked.
COMMON_MODEL_DIR="/data/aa/redis-2.7.1"
sys.path.append(COMMON_MODEL_DIR)
import redis
And when i set up crontab ,
*/10 1-23 * * * (cd /data3/aa/; python step.py 2 >> /data3/aa/2.log 2>&1)
But it won't worked it will report
Traceback (most recent call last):
File "step.py", line 11, in ?
import redis
File "/data/aa/redis-2.7.1/redis/__init__.py", line 1, in ?
from redis.client import Redis, StrictRedis
File "/data/aa/redis-2.7.1/redis/client.py", line 157
response = [nativestr(i) if i is not None else None for i in response]
^
SyntaxError: invalid syntax
How will i fix it?
Answer: Obviously the user account under which your cron job is running is using
another (and quite old) Python version that doesn't support ternary
expressions. Find out which Python _you_ are using and pass the full path in
your crontab.
|
Python realtime plotting
Question: I acquire some data in two arrays: one for the time, and one for the value.
When I reach 1000 points, I trigger a signal and plot these points (x=time,
y=value).
I need to keep on the same figure the previous plots, but only a reasonable
number to avoid slowing down the process. For example, I would like to keep
10,000 points on my graph. The matplotlib interactive plot works fine, but I
don't know how to erase the first points and it slows my computer very
quickly. I looked into matplotlib.animation, but it only seems to repeat the
same plot, and not really actualise it.
I'm really looking for a light solution, to avoid any slowing.
As I acquire for a very large amount of time, I erase the input data on every
loop (the 1001st point is stored in the 1st row and so on).
Here is what I have for now, but it keeps all the points on the graph:
import matplotlib.pyplot as plt
def init_plot():
plt.ion()
plt.figure()
plt.title("Test d\'acqusition", fontsize=20)
plt.xlabel("Temps(s)", fontsize=20)
plt.ylabel("Tension (V)", fontsize=20)
plt.grid(True)
def continuous_plot(x, fx, x2, fx2):
plt.plot(x, fx, 'bo', markersize=1)
plt.plot(x2, fx2, 'ro', markersize=1)
plt.draw()
I call the init function once, and the continous_plot is in a process, called
every time I have 1000 points in my array.
Answer: The lightest solution you may have is to replace the X and Y values of an
existing plot. (Or the Y value only, if your X data does not change. A simple
example:
import matplotlib.pyplot as plt
import numpy as np
import time
fig = plt.figure()
ax = fig.add_subplot(111)
# some X and Y data
x = np.arange(10000)
y = np.random.randn(10000)
li, = ax.plot(x, y)
# draw and show it
fig.canvas.draw()
plt.show(block=False)
# loop to update the data
while True:
try:
y[:-10] = y[10:]
y[-10:] = np.random.randn(10)
# set the new data
li.set_ydata(y)
fig.canvas.draw()
time.sleep(0.01)
except KeyboardInterrupt:
break
This solution is quite fast, as well. The maximum speed of the above code is
100 redraws per second (limited by the `time.sleep`), I get around 70-80,
which means that one redraw takes around 4 ms. But YMMV depending on the
backend, etc.
|
xpath in python does not grab entire HTML block
Question: I am using scrapy to scrape information off of a website. My xpath is working
but it does not grab information from block.
Python code:
sel.xpath('//div[@class="content"]/div/blockquote/node()').extract()[0]
I am using this to grab the first blockquote on the page. It cuts off after
there is a `<br>`.
For example:
If I can see this:
<blockquote class="postcontent restore ">
4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)
<br>
Operating System
<br>
Windows 8.1 64
<br>
Display
</blockquote>
It will only return:
> 4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)
But I would prefer it return everything, including html tags and the rest of
the text in blockquote.
Answer: `//div[@class="content"]/div/blockquote/node()` will get you all nodes just
under _a_ `blockquote`, children text nodes and element nodes.
In your case, you'll get the text nodes and the `<br>`s
`sel.xpath('//div[@class="content"]/div/blockquote/node()').extract()[0]` will
extract only the 1st node, which is the text node with "4th Generation Intel
Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)"
Here's a sample ipython session to show different outputs using selectors:
$ ipython
Python 2.7.6 (default, Mar 22 2014, 22:59:56)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: import scrapy
In [2]: selector = scrapy.selector.Selector(text="""<blockquote class="postcontent restore ">
...: 4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)
...: <br>
...: Operating System
...: <br>
...: Windows 8.1 64
...: <br>
...: Display
...: </blockquote>""")
In [3]: selector.xpath('blockquote/node()').extract()
Out[3]: []
In [4]: selector.xpath('.//blockquote/node()').extract()
Out[4]:
[u'\n4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)\n',
u'<br>',
u'\nOperating System\n',
u'<br>',
u'\nWindows 8.1 64\n',
u'<br>',
u'\nDisplay\n']
In [5]: selector.xpath('.//blockquote').extract()
Out[5]: [u'<blockquote class="postcontent restore ">\n4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)\n<br>\nOperating System\n<br>\nWindows 8.1 64\n<br>\nDisplay\n</blockquote>']
In [6]: selector.xpath('string(.//blockquote)').extract()
Out[6]: [u'\n4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)\n\nOperating System\n\nWindows 8.1 64\n\nDisplay\n']
In [7]: selector.xpath('.//blockquote//text()').extract()
Out[7]:
[u'\n4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)\n',
u'\nOperating System\n',
u'\nWindows 8.1 64\n',
u'\nDisplay\n']
In [8]: "\n".join(selector.xpath('.//blockquote//text()').extract())
Out[8]: u'\n4th Generation Intel Core i7-4710HQ Processor (2.50GHz 1600MHz 6MB)\n\n\nOperating System\n\n\nWindows 8.1 64\n\n\nDisplay\n'
In [9]:
* * *
After OP's comment, a good fit would be
`(//div[@class="content"]/div/blockquote)[1]//text()`
Using the OP's original input page:
$ scrapy shell http://forums.redflagdeals.com/dominos-pizza-50-off-july-14th-20th-1505545/
2014-07-16 20:43:45+0200 [scrapy] INFO: Scrapy 0.24.2 started (bot: scrapybot)
2014-07-16 20:43:45+0200 [scrapy] INFO: Optional features available: ssl, http11, boto
2014-07-16 20:43:45+0200 [scrapy] INFO: Overridden settings: {'LOGSTATS_INTERVAL': 0}
2014-07-16 20:43:45+0200 [scrapy] INFO: Enabled extensions: TelnetConsole, CloseSpider, WebService, CoreStats, SpiderState
2014-07-16 20:43:46+0200 [scrapy] INFO: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, MetaRefreshMiddleware, HttpCompressionMiddleware, RedirectMiddleware, CookiesMiddleware, ChunkedTransferMiddleware, DownloaderStats
2014-07-16 20:43:46+0200 [scrapy] INFO: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2014-07-16 20:43:46+0200 [scrapy] INFO: Enabled item pipelines:
2014-07-16 20:43:46+0200 [scrapy] DEBUG: Telnet console listening on 127.0.0.1:6023
2014-07-16 20:43:46+0200 [scrapy] DEBUG: Web service listening on 127.0.0.1:6080
2014-07-16 20:43:46+0200 [default] INFO: Spider opened
2014-07-16 20:43:47+0200 [default] DEBUG: Crawled (200) <GET http://forums.redflagdeals.com/dominos-pizza-50-off-july-14th-20th-1505545/> (referer: None)
[s] Available Scrapy objects:
[s] crawler <scrapy.crawler.Crawler object at 0x7f63775b0c10>
[s] item {}
[s] request <GET http://forums.redflagdeals.com/dominos-pizza-50-off-july-14th-20th-1505545/>
[s] response <200 http://forums.redflagdeals.com/dominos-pizza-50-off-july-14th-20th-1505545/>
[s] settings <scrapy.settings.Settings object at 0x7f6377c4fd90>
[s] spider <Spider 'default' at 0x7f6376d52bd0>
[s] Useful shortcuts:
[s] shelp() Shell help (print this help)
[s] fetch(req_or_url) Fetch request (or URL) and update local objects
[s] view(response) View response in a browser
In [1]: response.xpath('//div[@class="content"]/div/blockquote')
Out[1]:
[<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>,
<Selector xpath='//div[@class="content"]/div/blockquote' data=u'<blockquote class="postcontent restore "'>]
In [2]: response.xpath('(//div[@class="content"]/div/blockquote)[1]')
Out[2]: [<Selector xpath='(//div[@class="content"]/div/blockquote)[1]' data=u'<blockquote class="postcontent restore "'>]
In [3]: response.xpath('(//div[@class="content"]/div/blockquote)[1]//text()')
Out[3]:
[<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n\t\t\t\tGot a coupon that stated 50% off a'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\nCode is CAG5014'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\nDeal is on! '>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u"Don't Forget to tip driver!!">,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n'>,
<Selector xpath='(//div[@class="content"]/div/blockquote)[1]//text()' data=u'\r\n\t\t\t'>]
In [4]: response.xpath('string((//div[@class="content"]/div/blockquote)[1])').extract()
Out[4]: [u"\r\n\t\t\t\tGot a coupon that stated 50% off any pizza at menu price. \r\n\r\nCode is CAG5014\r\n\r\nDeal is on! \r\n\r\nDon't Forget to tip driver!!\r\n\r\n\r\n\t\t\t"]
In [5]: response.xpath('normalize-space((//div[@class="content"]/div/blockquote)[1])').extract()
Out[5]: [u"Got a coupon that stated 50% off any pizza at menu price. Code is CAG5014 Deal is on! Don't Forget to tip driver!!"]
In [6]:
|
Comparing two csv files in Python
Question: I have this program that takes two csv files into consideration. It looks at
"testclaims" (one column many rows) and sees if any words in "masterlist"(one
column, many rows) are within the rows of "testclaims." If the rows in
"testclaims" contains any word in "masterlist" it will list it into a new .csv
file called "output." This part of the program works great.
The part that I can't seem to figure out is to output all the remaining rows
in "testclaims" that don't contain ANY words in "masterlist" into another csv
called "output2" I would think that the last two lines of my code should get
this to work, but it's not outputting what I want. I hope I've explained this
clearly enough. Here's my code:
import csv
with open("testclaims.csv") as file1, open("masterlist.csv") as file2,
open("stopwords.csv") as file3,\
open("output.csv", "wb+") as file4, open("output2.csv", "wb+") as file5:
writer = csv.writer(file4)
writer2 = csv.writer(file5)
key_words = [word.strip() for word in file2.readlines()]
stop_words = [word.strip() for word in file3.readlines()]
internal_stop_words = [' a ', ' an ', ' and ', 'as ', ' at ', ' be ', 'ed ',
'ers ', ' for ',\
' he ', ' if ', ' in ', ' is ', ' it ', ' of ', ' on ', ' to ', 'her ', 'hers '\
' do ', ' did ', ' a ', ' b ', ' c ', ' d ', ' e ', ' f ', ' g ', ' h ', ' i ',\
' j ', ' k ', ' l ', ' m ', 'n ', ' n', ' nc ' ' o ', ' p ', ' q ', ' r ', ' s ',\
' t ', ' u ', ' v ', ' w ', ' x ', ' y ', 'z ', ',', '"', 'ers ', ' th ', ' gc ',\
' so ', ' ot ', ' ft ', ' ow ', ' ir ', ' ho ', ' er ', ]
for row in file1:
row = row.strip()
row = row.lower()
for stop in stop_words:
if stop in row:
row = row.replace(stop," ")
for stopword in internal_stop_words:
if stopword in row:
row = row.replace(stopword," ")
for key in key_words:
if key in row:
writer.writerow([key, row])
elif key not in row:
writer2.writerow([row])
What output2 is outputting is every row in "testclaims" repeated multiple
times.
For example if "testclaims" contains this one column:
Happy
Sad
Angry
Dog
Cat
"output2" is outputting a csv that prints this one column:
Happy
Happy
Happy
Happy
Happy
Sad
Sad
Sad
Sad
Angry
Angry
Angry
Angry
Angry
Dog
Dog
Dog
Dog
Dog
Cat
Cat
Cat
Cat
Cat
And it doesn't output the same number of each row either.
Answer: you have a double for loop and each time you print the row, but you only want
it at most once per row. you should adjust your last two lines:
for row in file1:
...
for key in key_words:
if key in row:
writer.writerow([key, row])
if not any(key in row for key in key_words):
writer2.writerow([row])
|
ValueError: invalid literal for float(): Timestep:
Question: I have a program that finds some data and runs a basic math function on the
data, but when I run it I get the following error: `ValueError: invalid
literal for float(): Timestep:`. The error occurs in line where I call
`map(float,line.split()[1:])`.
Does anyone know why and how to fix this error.
#!/usr/bin/python
l=[]
with open("movie.xyz") as f:
line = f.next()
nat = int(line.split()[0])
print nat
f.next()# skip headers
for line in f:
if line.strip():
l.append(map(float,line.split()[1:])) # make all values floats
#print l[0][0]
b = 0
a = 1
for b in range(55):
for a in range(b+1,56):
import operator
import numpy as np
#vector1 = l[b]
vector1 = (l[b][0],l[b][1],l[b][2])
vector2 = (l[a][0],l[a][1],l[a][2])
#print('vector 1 = %' % vector1)
#print('vector 1 = (%f,%f,%f)' % vector1)
#print vector2
x = vector1
y = vector2
vector3 = list(np.array(x) - np.array(y))
#print vector3
dotProduct = reduce( operator.add, map( operator.mul, vector3, vector3))
dp = dotProduct**.5
print dp
first couple lines of data look like:
2805
Atoms. Timestep: 0
Cu 46.7176 27.1121 27.1121
Cu 43.2505 36.0618 32.4879
Cu 43.3392 36.0964 28.9236
Cu 43.2509 37.8362 27.1091
Cu 43.3406 36.0958 25.2957
Cu 43.2582 36.0629 21.737
Cu 43.2505 32.4879 36.0618
Answer: insert
import pdb; pdb.set_trace()
before this line and see what gives you `line.split()[1:]`
pdb = prompt debugger: <https://docs.python.org/2/library/pdb.html>
or do this:
if line.strip():
try:
l.append(map(float,line.split()[1:]))
except ValueError:
print "Value error at: ", line.split()[1:]
## #
to make this code work add this function:
def foo(value):
try:
result = float(value)
except ValueError:
print "cant parse %r into float" %value
result = None
return result
and replace the line:
l.append(map(float,line.split()[1:]))
to:
l.append(map(foo, line.split()[1:]))
|
Calculate the Cumulative Distribution Function (CDF) in Python
Question: How can I calculate in python the [Cumulative Distribution Function
(CDF)](https://en.wikipedia.org/wiki/Cumulative_distribution_function)?
I want to calculate it from an array of points I have (discrete distribution),
not with the continuous distributions that, for example, scipy has.
Answer: (It is possible that my interpretation of the question is wrong. If the
question is how to get from a discrete PDF into a discrete CDF, then
`np.cumsum` divided by a suitable constant will do if the samples are
equispaced. If the array is not equispaced, then `np.cumsum` of the array
multiplied by the distances between the points will do.)
If you have a discrete array of samples, and you would like to know the CDF of
the sample, then you can just sort the array. If you look at the sorted
result, you'll realize that the smallest value represents 0% , and largest
value represents 100 %. If you want to know the value at 50 % of the
distribution, just look at the array element which is in the middle of the
sorted array.
Let us have a closer look at this with a simple example:
import matplotlib.pyplot as plt
import numpy as np
# create some randomly ddistributed data:
data = np.random.randn(10000)
# sort the data:
data_sorted = np.sort(data)
# calculate the proportional values of samples
p = 1. * arange(len(data)) / (len(data) - 1)
# plot the sorted data:
fig = figure()
ax1 = fig.add_subplot(121)
ax1.plot(p, data_sorted)
ax1.set_xlabel('$p$')
ax1.set_ylabel('$x$')
ax2 = fig.add_subplot(122)
ax2.plot(data_sorted, p)
ax2.set_xlabel('$x$')
ax2.set_ylabel('$p$')
This gives the following plot where the right-hand-side plot is the
traditional cumulative distribution function. It should reflect the CDF of the
process behind the points, but naturally it is not the as long as the number
of points is finite.
This function is easy to invert, and it depends on your application which form
you need.
|
Connect Android App to Python script on Mac OS X via Bluetooth
Question: My goal is very basic. I am trying to transmit a String from my android device
to my Mac running OSX 10.9 via bluetooth. On my Mac I am using the lightblue
python library to do the connections. I am pretty sure that the issue is
raised by a cast-like exception between what methods are expecting (more
detail below). I am relatively new to this type of networking. This is
ultimately going to become a rough proof of concept. Any advice would work as
well.
Thanks!
Android Code (Sending String):
public class Main extends Activity {
private OutputStream outputStream;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
try {
init();
write("Test");
} catch (IOException e) {
e.printStackTrace();
}
}
private void init() throws IOException {
BluetoothAdapter blueAdapter = BluetoothAdapter.getDefaultAdapter();
if (blueAdapter != null) {
if (blueAdapter.isEnabled()) {
Set<BluetoothDevice> bondedDevices = blueAdapter.getBondedDevices();
if(bondedDevices.size() > 0){
BluetoothDevice device = (BluetoothDevice) bondedDevices.toArray()[0];
ParcelUuid[] uuids = device.getUuids();
BluetoothSocket socket = device.createRfcommSocketToServiceRecord(uuids[0].getUuid());
socket.connect();
outputStream = socket.getOutputStream();
}
Log.e("error", "No appropriate paired devices.");
}else{
Log.e("error", "Bluetooth is disabled.");
}
}
}
public void write(String s) throws IOException {
outputStream.write(s.getBytes());
}
public void run() {
final int BUFFER_SIZE = 1024;
byte[] buffer = new byte[BUFFER_SIZE];
int bytes = 0;
while (true) {
try {
bytes = inStream.read(buffer, bytes, BUFFER_SIZE - bytes);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Adapted from: [Android sample bluetooth code to send a simple string via
bluetooth](http://stackoverflow.com/questions/22899475/android-sample-
bluetooth-code-to-send-a-simple-string-via-bluetooth)
Python LightBlue Example Code (Receiving String):
import lightblue
# create and set up server socket
sock = lightblue.socket()
sock.bind(("", 0)) # bind to 0 to bind to a dynamically assigned channel
sock.listen(1)
lightblue.advertise("EchoService", sock, lightblue.RFCOMM)
print "Advertised and listening on channel %d..." % sock.getsockname()[1]
conn, addr = sock.accept()
print "Connected by", addr
data = conn.recv(1024) #CRASHES HERE
print "Echoing received data:", data
# sometimes the data isn't sent if the connection is closed immediately after
# the call to send(), so wait a second
import time
time.sleep(1)
conn.close()
sock.close()
Error in console:
python test.py
Advertised and listening on channel 1...
Connected by ('78:52:1A:69:B2:6D', 1)
Traceback (most recent call last):
File "test.py", line 16, in <module>
data = conn.recv(1024)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/lightblue/_bluetoothsockets.py", line 470, in recv
return self.__incomingdata.read(bufsize)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/lightblue/_bluetoothsockets.py", line 150, in read
self._build_str()
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/lightblue/_bluetoothsockets.py", line 135, in _build_str
new_string = "".join(self.l_buffer)
TypeError: sequence item 0: expected string, memoryview found
The last line is where I am pretty sure I am messing up. It is expecting a
string, but I am pretty sure I am not sending a memoryview (as far as I am
aware).
Answer: In your Android part, you're better off using
[DataOutputStream](http://developer.android.com/reference/java/io/DataOutputStream.html)
to send string. Do it like this:
public void write(String s) throws IOException {
// outputStream.write(s.getBytes());
// Wrap the OutputStream with DataOutputStream
DataOutputStream dOut = new DataOutputStream(outputStream);
// Encode the string with UTF-8
byte[] message = s.getBytes("UTF-8");
// Send it out
dOut.write(message, 0, message.length);
}
* * *
Further reading: [MUTF-8 (Modified UTF-8)
Encoding](http://developer.android.com/reference/java/io/DataInput.html)
|
How to extract the price from html using regex in python
Question: I have a html output that contains this:
<span class="value">
Price:<br>
<span style="color:white">23,07€ </span>
</span>
I tried to extract the prices using:
prices = re.findall(r'<span class="value">.*?(\d{1,3}\.?\d{1,2}).*?</span>',search_result)
sometimes the decimals are replaced with -- when there are 00, also i need
this 2 numbers that get extracted by the expression 23 07 joined 2307
Thank you for your time.
Answer: Get the matched group from index 1.
(?<=>)(\d[^€]*)
[demo](http://regex101.com/r/rI6yA4/5)
* * *
OR get the matched group index 1 and 2 for each number
(?<=>)(\d+)\D(\d+)\D
[demo](http://regex101.com/r/rI6yA4/7)
* * *
If you are interested only for `<span>` tag then try below regex
<span [^>]*>(\d+)\D(\d+)\D[^<]*
[demo](http://regex101.com/r/rI6yA4/12)
Sample code:
import re
p = re.compile(ur'<span [^>]*>(\d+)\D(\d+)\D[^<]*')
test_str = u"..."
re.findall(p, test_str)
|
Split long string of addresses into list of addresses in Python
Question: I have a string of a couple thousand addresses in python, like such:
`'123 Chestnut Way 4567 Oak Lane 890 South Pine Court'`
What is the easiest way to split this long string into separate addresses? I'm
trying to write a program that splits based on 3 or 4 characters in a row
where `47 < ord(i) < 58`, but I'm having trouble.
Answer: Assuming all of the addresses are like those given, you can use
[`re.findall`](https://docs.python.org/2/library/re.html#re.findall):
>>> from re import findall
>>> string = '123 Chestnut Way 4567 Oak Lane 890 South Pine Court'
>>> findall("\d+\D+(?=\s\d|$)", string)
['123 Chestnut Way', '4567 Oak Lane', '890 South Pine Court']
>>>
All of the Regex syntax used above is explained
[here](https://docs.python.org/2/library/re.html#regular-expression-syntax),
but below is a quick breakdown:
\d+ # One or more digits
\D+ # One or more non-digits
(?= # The start of a lookahead assertion
\s # A space
\d|$ # A digit or the end of the string
) # The end of the lookahead assertion
|
How to give the folder name using model instance in django
Question: New to python . Anyway I am on my way to first project.
See i need to upload multiple file into single folder so i come up with an
idea like this.
folder_name1
------myfiles1.jpg
------myfiled2.jpg
folder_name2
------mynewfiles.jpg
------mynewfiles1.jpg
And i read lot of tutorials this is my models.py
def content_file_name(instance, filename):
return "uploads/{folder}/{file}".format(id=instance, folder=instance.albumname, file=filename)
class Album(models.Model):
albumname = models.CharField(max_length=100)
audiofile = models.FileField(upload_to=content_file_name)#documents/%Y/%m/%d
Updated: This is my view.py
def viewalbum(request):
if request.method == 'POST':
form = AlbumForm(request.POST, request.FILES)
if form.is_valid():
alubmnew = Album()
albumvalue = Album()
albumnew = Album(albumname = request.POST.get('albumname', None))
albumvalue = Album(audiofile = request.FILES['audiofile'])
#for albumvalue in request.FILES.getlist('audiofile'):
albumvalue.save()
albumnew.save()
return HttpResponseRedirect(reverse('google.views.viewalbum'))
else:
form = AlbumForm()
return render_to_response('audio/test.html',{'form': form}, context_instance=RequestContext(request))
The problem i am having right now is.. It doesn`t create albumname folder
And also in my form i can`t able to upload multiple file in single time. Its
actually takes only one file to upload...
Answer:
import os
def content_file_name(instance, filename):
upload_dir = os.path.join('uploads', instance.albumname)
if not os.path.exists(upload_dir):
os.makedirs(upload_dir)
return os.path.join(upload_dir, filename)
|
After 12 requests (~60 sec) Firebase or Python-firebasin library do not send and receive data
Question: I have a problem, please help me.
I created Python script what is collaborating with Firebase to save and
receive data. My script works with python-firebasin library ([link to python-
firebasin](https://github.com/abeisgreat/python-firebasin)). I tested my
application one week with my Firebase account - HACKER PLAN. All works fine
all this time. After that i buy premium account with special URL like
x.firebaseio.com here begins my problems. I import json structure from my old
firebase to my new firebase account and set in my Python script new firebase
URL to my new firebase account. So now all must works fine with my new
firebase premium account. I run my script and ~60 seconds my script works
fine. Callback events work, set values works. But after ~60 seconds Firebase
do not receive and do not send any callback to my Python script. For debugging
i wrote simple script what send unixtime to firebase every 5 second. So all
works fine first 12 requests (12 * 5 = ~60 sec), after what firebase do not
receive any data. Python do not send any error and callback too. Atention: All
works fine with my old Firebase account - HACKER PLAN!
from firebasin import Firebase
from time import sleep, time
# Firebase
vGFirebase = None
vGCompanyId = '1'
vGHardwareId = '0000000000123123'
i = 1
vGFirebase = Firebase('https://subdomain.firebaseio.com')
def errorCallback(data):
print('errorCallback', data)
while True:
try:
pingChild = vGFirebase.child('data/app/pings/' + str(vGCompanyId) + '/' + str(vGHardwareId))
sendTime = int(time())
pingChild.set(sendTime, errorCallback)
print(i, 'send ', sendTime)
i += 1
sleep(5)
except:
print('Exception')
break
vGFirebase.waitForInterrupt()
I enable Debug mode in python-firebasin library. So after 12 requests i got
this message: **(('Closed down :(', 1006, 'Going away'),)** So i think this is
because Firebase close connection... But why?
Sorry for my bad english...
Answer: firebasin does not start a Heartbeat to keep the connection alive. You can
easily start one yourself. After the line creating `vGFirebase`:
from ws4py.websocket import Heartbeat
while not vGFirebase.connection.data:
sleep(1)
Heartbeat(vGFirebase.connection.data,2).start()
Unfortunately, the _keep_alive method in dataref.py seems to not get along
with hacker plans and causes them to disconnect when it fires its own
keepalive message, so you'll also need to disable that. You can do so on the
fly by adding
import firebasin
firebasin.dataref.RootDataRef._keep_alive = lambda *x: None
to the top of your script. A more permanent, but non-portable solution would
be to patch dataref.py to replace it's _keep_alive method with one that starts
ws4py's Heartbeat. I've submitted a pull request to do that upstream; we'll
see if there is a reason Abe Haskins didn't do it that way in the first place.
|
subprocess.call and tar -zxvf
Question: I am trying to call this command `tar -zxvf file.tar.gz` from a python script
and I'm having trouble with it. I've read some relevant q/a's but I still
haven't figured out how to do it.
I was thinking to fit my code to the original command:
subprocess.check_call(args, *, stdin=None, stdout=None, stderr=None, shell=False)
So far I've made several attempts, as shown below
stdin = file.tar.gz
subprocess.check_call(-zxvf, stdin)
Any help? Thanks.
Answer: You can untar a file using the `tarfile` module
import tarfile
tar = tarfile.open("sample.tar.gz")
tar.extractall()
tar.close()
|
Test to see if URL exists
Question: What is the best way to test if a URL exists in python, I currently use cURL
however I wanted to switch to use python
In cURL I use something like
curl http://www.google.com | tidy -i
together with a bash script
Answer: The quickest way is probably something like
import httplib
try:
url = httplib.HTTPConnection('yahoo.com')
url.connect()
except httplib.HTTPException as ex:
print "not connected"
|
Should logger.exception only be called inside an except block? Why?
Question: The docs for
[`logger.exception`](https://docs.python.org/2/library/logging.html#logging.Logger.exception)
mention:
> This method should only be called from an exception handler.
So usage should be somethnig like this:
import logging, sys
logger = logging.getLogger()
logger.setLevel(logging.DEBUG)
handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.DEBUG)
logger.addHandler(handler)
try:
errorerrorerror
except NameError as e:
logger.exception('debug message 1 {}'.format(e))
But when I tried doing it the "wrong" way, behaviour seemed to be just the
same:
try:
errorerrorerror
except NameError as e:
pass
logger.exception('debug message 2 {}'.format(e))
What is the reason for that caveat mentioned in the docs? Is it _actually_
true that we can only use it in an except block, for some subtle reason not
evident here?
I am aware that in python 3 this has changed, but python documentation is
usually very consistent in mentioning these differences..
Answer: The method is _designed_ for use in an exception handler. As such the
documentation tells you this, by using the word _should_ , not _must_.
In the text of standards, _should_ and _must_ are rigidly defined; one means
_we advice you to do it this way, it'd be much better if you did_ , the other
means _it's an outright error if you don't do this_. See [RFC
2119](http://www.ietf.org/rfc/rfc2119.txt) for the IETF taskforce wording.
All `logging.exception()` does is set the `exc_info` keyword argument before
calling `logging.error()`. The `exc_info` argument is then later fleshed out
to include the _most recently handled exception_ , taken from
[`sys.exc_info()`](https://docs.python.org/2/library/sys.html#sys.exc_info).
It is then up to the formatter to include the exception message (via the
[`Formatter.format_exception()`
method](https://docs.python.org/2/library/logging.html#logging.Formatter.formatException)
to format the exception.
Because `sys.exc_info()` works both in the `except` suite and out, both
variants work. From a _code documentation point of view_ , it is just clearer
if you use it in the `except` handler.
You don't need to include the error message, really, because your log
formatter should already do that for you:
logger.exception('debug message 2') # exception should be included automatically
You can explicitly attach an exception to any log message with:
logger.error('debug message 2', exc_info=sys.exc_info())
or any other 3-tuple value with the exception type, the exception value and a
traceback. Alternatively, set `exc_info=1` to have the logger retrieve the
information from `sys.exc_info()` itself.
See the documentation for
[`Logger.debug()`](https://docs.python.org/2/library/logging.html#logging.Logger.debug):
> _exc_info_ which, if it does not evaluate as false, causes exception
> information to be added to the logging message. If an exception tuple (in
> the format returned by `sys.exc_info()`) is provided, it is used; otherwise,
> `sys.exc_info()` is called to get the exception information.
|
python matplotlib imshow with difference lenghts in data-array
Question: Is there a way to plot heat map with different row lengths using matplotlib?
like this:
plt.imshow( [ [1,2,3], [1,2], [1,2,3,4,5,6,7], [1,2,3,4]])
plt.jet()
plt.colorbar()
plt.show()
[Desired image](http://postimg.org/image/geoa9nrxf/)
Answer: Given the desired image, I think you will want to you `plt.pcolormesh` rather
than `imshow` but I may be wrong. In any case I personally would create a
function to pad the array then use a mask so that `imshow` or `pcolormesh`
will not plot those points. For example
import matplotlib.pylab as plt
import numpy as np
def regularise_array(arr, val=-1):
""" Takes irregular array and returns regularised masked array
This first pads the irregular awway *arr* with values *val* to make
it of rectangular. It then applies a mask so that the padded values
are not displayed by pcolormesh. For this reason val should not
be in *arr* as you will loose these points.
"""
lengths = [len(d) for d in data]
max_length = max(lengths)
reg_array = np.zeros(shape=(arr.size, max_length))
for i in np.arange(arr.size):
reg_array[i] = np.append(arr[i], np.zeros(max_length-lengths[i])+val)
reg_array = np.ma.masked_array(reg_array, reg_array == val)
return reg_array
data = np.array([[1,2,3], [1,2], [1,2,3,4,5,6,7], [1,2,3,4]])
reg_data = regularise_array(data, val=-1)
plt.pcolormesh(reg_data)
plt.jet()
plt.colorbar()
plt.show()
The issue with this is you need to take care thet `val` is not in the array.
You could add a simple check for this or base it on the data you are using.
The for loop could probably be vectorised but I cannot work out how.
|
Fetch time from mysql using python
Question: I am using the code below to fetch time entity called `fajr_begins` from
`mysql`. I am able to print `fajr_begins` which is in the format: 5:27:00, how
can i convert this to a time format in python, so that i can manipulate the
time and add 15mins?
cnx = mysql.connector.connect(host=mysql_remote_host, user=mysql_remote_host_user, password=mysql_remote_host_password, database=mysql_remote_host_database)
cursor = cnx.cursor()
cursor.execute("select * from prayertimes where DATE(date) = DATE(NOW())" )
results = cursor.fetchall()
id, date, fajr_begins, fajr_jamaat, sunrise, zuhr_begins, zuhr_jamaat, asr_begins, asr_jamaat, maghrib_jamaat, isha_begins, isha_jamaat = results[0]
cursor.close()
print fajr_begins
Answer: You have to convert it using
[`strptime`](https://docs.python.org/2/library/datetime.html#datetime.datetime.strptime).
`timedelta` will be use for adding minutes.
>>> from datetime import datetime, timedelta
>>> a = "05:27:00"
>>> b = datetime.strptime(a, "%H:%M:%S")
>>> print b
1900-01-01 05:27:00
>>> c = timedelta(minutes=15)
>>> print c
0:15:00
>>> print b+c
1900-01-01 05:42:00
|
Python pandas how to get the reverse of groupby
Question: I have two data frames. They are the same except for one column. I want to
change the column of the second dataframe according to mean values from the
first dataframe. For the latter I have to use groupby, but then I don't know
how to get a reverse. Below is a minimal example, where in this particular
example df_two should end up being the same as df_one. My question is how to
get from tmp to df2_new - see the code below.
import pandas as pd
def foo(df1, df2):
# Group by A
groupsA_one = dict(list(df1.groupby('A', as_index=False)))
groupsA_two = dict(list(df2.groupby('A', as_index=False)))
for key_A in groupsA_one:
# Group by B
groupsB_one = dict(list(groupsA_one[key_A].groupby('B', as_index=False)))
groupsB_two = dict(list(groupsA_two[key_A].groupby('B', as_index=False)))
for key_B in groupsB_one:
# Group by C
tmp = groupsB_two[key_B].groupby('C', as_index=False)['D'].mean() # Returns DataFrame with NaN
tmp['D'] = groupsB_one[key_B].groupby('C', as_index=False)['D'].mean()['D']
print tmp
df2_new = [] # ???
return df2_new
if __name__ == '__main__':
A1 = {'A': [1, 1, 1, 1, 2, 2, 2, 2], 'B': [1, 1, 2, 2, 1, 1, 2, 2],
'C': [1, 2, 1, 2, 1, 2, 1, 2], 'D': [5, 5, 5, 5, 5, 5, 5, 5]}
A2 = {'A': [1, 1, 1, 1, 2, 2, 2, 2], 'B': [1, 1, 2, 2, 1, 1, 2, 2],
'C': [1, 2, 1, 2, 1, 2, 1, 2], 'D': [0, 0, 0, 0, 0, 0, 0, 0]}
df_one = pd.DataFrame(A1)
df_two = pd.DataFrame(A2)
foo(df_one, df_two)
Answer: Here is the solution that I wanted. Please, if you find a more elegant
solution I will be happy to set it as a correct answer.
Hre it is:
import pandas as pd
import numpy as np
def foo(df):
# Group by A
groups_a_one = dict(list(df.groupby('A', as_index=False)))
for key_a in groups_a_one:
# Group by B
groups_b_one = dict(list(groups_a_one[key_a].groupby('B', as_index=False)))
for key_b in groups_b_one:
# Group by C
tmp = groups_b_one[key_b].groupby('C', as_index=False).transform(lambda x: x.fillna(x.mean()))
df.ix[tmp.index, 'D'] = tmp['D']# assign mean values to correct lines in df
return df
if __name__ == '__main__':
A1 = {'A': [1, 1, 1, 1, 2, 2, 2, 2], 'B': [1, 1, 2, 2, 1, 1, 2, 2],
'C': [1, 2, 1, 2, 1, 2, 1, 2], 'D': [5, 5, 5, 5, 5, 5, 5, 5]}
A2 = {'A': [1, 1, 1, 1, 2, 2, 2, 2], 'B': [1, 1, 2, 2, 1, 1, 2, 2],
'C': [1, 2, 1, 2, 1, 2, 1, 2], 'D': [np.NaN, np.NaN, np.NaN, np.NaN, np.NaN, np.NaN, np.NaN, np.NaN]}
df_one = pd.DataFrame(A1)
df_two = pd.DataFrame(A2)
df = pd.concat([df_one, df_two], axis=0, ignore_index=True)# To get only one DataFrame
# run the transform
foo(df)
Here is the initial state and the final one:
# Initial
A B C D
0 1 1 1 5
1 1 1 2 5
2 1 2 1 5
3 1 2 2 5
4 2 1 1 5
5 2 1 2 5
6 2 2 1 5
7 2 2 2 5
8 1 1 1 NaN
9 1 1 2 NaN
10 1 2 1 NaN
11 1 2 2 NaN
12 2 1 1 NaN
13 2 1 2 NaN
14 2 2 1 NaN
15 2 2 2 NaN
# Final
A B C D
0 1 1 1 5
1 1 1 2 5
2 1 2 1 5
3 1 2 2 5
4 2 1 1 5
5 2 1 2 5
6 2 2 1 5
7 2 2 2 5
8 1 1 1 5
9 1 1 2 5
10 1 2 1 5
11 1 2 2 5
12 2 1 1 5
13 2 1 2 5
14 2 2 1 5
15 2 2 2 5
|
Detecting and Comparing GPIO events in Beaglebone using Python
Question: I am trying to detect two events in two different GPIOs in the Beaglebone
Black, and then decide which one happened first. I am using Adafruit_BBIO.GPIO
for the code which is written in Python. It is not working properly, and have
no idea why. Here is the code:
import sys
import thread
import time
from datetime import datetime
import bitarray
import Adafruit_BBIO.GPIO as GPIO
gpio_state = [0, 0]
gpio_time = [0, 0]
ir_recv = ['GPIO0_26', 'GPIO1_12']
def checkEvent(index):
while True:
if GPIO.event_detected(ir_recv[index]):
if (gpio_state[index] == 0):
gpio_state[index] = 1
gpio_time[index] = datetime.now()
print ir_recv[index]
time.sleep(5) # time to avoid rebounces
for gpio in ir_recv:
GPIO.setup(gpio, GPIO.IN)
GPIO.add_event_detect(gpio, GPIO.RISING)
try:
thread.start_new_thread(checkEvent, (0, ) )
thread.start_new_thread(checkEvent, (1, ) )
except:
print "Error: unable to start thread"
while True:
if (gpio_state[0] == 1) and (gpio_state[1] == 1):
if gpio_time[0] > gpio_time[1]:
print "1"
if gpio_time[0] < gpio_time[1]:
print "2"
if gpio_time[0] == gpio_time[1]:
print "???"
gpio_state[0] = 0
gpio_state[1] = 0
gpio_time[0] = 0
gpio_time[1] = 0
I don't get any error. The main problem is that the events are not compared
correctly, e.g. although event in GPIO0_26 happens first than the one in
GPIO1_12 (i.e. gpio_time[0] is smaller than gpio_time[1]), the output in the
last While loop does not print out "2". Also sometimes the code prints out
twice the GPIO pin from the threads.
Thanks in advance for any suggestion to find a solution.
Answer: I'd recommend using [PyBBIO](https://github.com/graycatlabs/PyBBIO) for this
(granted, I am the author). It has an interrupt API which is based on
[epoll](http://linux.die.net/man/4/epoll) (for kernel level interrupt
signalling), and would greatly simplify this. Something like this should do
the trick (I haven't tested it):
from datetime import datetime
from bbio import *
gpio_state = [0, 0]
gpio_time = [0, 0]
ir_recv = ['GPIO0_26', 'GPIO1_12']
def getInterrupt(index):
gpio_time[index] = datetime.now()
gpio_state[index] = 1
print "received interrupt from {} at {}".fomrat(ir_recv[index],
gpio_time[index]
)
def setup():
for i in range(len(ir_recv)):
pinMode(ir_recv[i], INPUT, pull=-1)
# The optional pull=-1 enables the internal pull-down resistor
attachInterrupt(ir_recv[0], lambda: getInterrupt(0), RISING)
attachInterrupt(ir_recv[1], lambda: getInterrupt(1), RISING)
def loop():
# You can do other stuff here while you're waiting...
delay(1000)
run(setup, loop)
And you should make sure your PyBBIO is up to date with:
# pip install -U PyBBIO
|
Get and count node neighbors Python
Question: I am trying to read a file with node pairs and weight. I have find the
neighbours of each pair individual and combined both also count them. Later
find the ratio of the neighbours that each node has. I am stuck with finding
nodes.
infile.txt
0_node1 0_node2 0w
1_node1 1_node2 1w
2_node1 2_node2 2w
3_node1 3_node2 3w
4_node1 4_node2 4w
Code:
import networkx as nx
import matplotlib.pyplot as plt
G=nx.Graph()
G = nx.read_edgelist('infile.txt', data=[("weight", float)])
def get_triangle(G):
for n1 in G.nodes:
neighbors1 = set(G[n1])
for n2 in filter(lambda x: x>n1, nodes):
neighbors2 = set(G[n2])
common = neighbors1 & neighbors2
for n3 in filter(lambda x: x>n2, common):
print n1
print n2
print n3
I did check the indentations in program does not seem to be problem. I not
getting the neighbours list.
Answer: If you are going to do anything with the values I suggest yield'ing a 3 node
tuple.
I had to change the data so the import would work (i stripped out the w's) and
there is support for finding triangle nodes in networkx which helps limit how
many objects we are iterating over each time.
infile.txt
0_node1 0_node2 0
1_node1 1_node2 1
2_node1 2_node2 2
3_node1 3_node2 3
4_node1 4_node2 4
0_node1 1_node2 5
0_node2 1_node2 6
0_node2 1_node1 7
code:
import networkx as nx
import itertools as it
def get_triangles(G):
def found_rotation(x):
for rotation in it.permutations(x):
if rotation in triangles_duplicates:
return 1
return 0
triangles = []
triangles_duplicates=[]
triangle_nodes = dict((x,nx.triangles(G,x)) for x in G.nodes() if nx.triangles(G,x) > 0)
for vertex1 in triangle_nodes:
vertex1_neighbors_that_are_triangles = set(G.neighbors(vertex1)).intersection( \
set(triangle_nodes) )
for vertex2 in vertex1_neighbors_that_are_triangles:
if triangle_nodes[vertex2] > 0:
vertex2_neighbors_that_are_triangles_and_not_vertex1 = \
set(G.neighbors(vertex2)).intersection(\
G.neighbors(vertex1))-{vertex1}-{vertex2}
for vertex3 in vertex2_neighbors_that_are_triangles_and_not_vertex1:
if triangle_nodes[vertex3]>0:
for z in G.neighbors(vertex3):
if (vertex1 == z) and not found_rotation((vertex1,vertex2,vertex3)):
triangle_nodes[vertex1] -=1
triangle_nodes[vertex2] -=1
triangle_nodes[vertex3] -=1
triangles.append((vertex1,vertex2,vertex3))
triangles_duplicates.append((vertex1,vertex2,vertex3))
return triangles
if __name__ == "__main__":
#G = nx.karate_club_graph()
G = nx.read_edgelist('this.txt', data=[("weight",int)])
With data like this the answer would be 2 triangles (or you could switch it
with karate_club_graph and get 45)
I'd be interested in seeing improvements if you do something with this.
|
python strip string from end the most greedily
Question: here it is:
str_ = 'file_.csv_.csv.bz2'
re.sub(regex, '', str_)
I want 'regex' value to get `'file_.csv_'` i.e. the file name without the
actual extension which here `'.csv.bz2'` and could be `'.csv.*'` while `.* =
''|bz2|gz|7z|`... any compression format.
More precisely I want `re.sub` to match from the end of `str_` the most
greedily. with `regex = '\.csv.*$'` I would get only `'file_'`.
I could of course do `os.path.splitext()` \- check if `str_` ends with
`'.csv'` \- `os.path.splitext()` if so, but is there a shorter way?
Answer: You could use `re.split()` splitting of the suffix:
result = re.split(r'\.csv(?:\.\w+)?$', filename)[0]
Demo:
>>> import re
>>> filename = 'file_.csv_.csv.bz2'
>>> re.split(r'\.csv(?:\.\w+)?$', filename)[0]
'file_.csv_'
>>> re.split(r'\.csv(?:\.\w+)?$', 'foobar_.csv_.csv')[0]
'foobar_.csv_'
>>> re.split(r'\.csv(?:\.\w+)?$', 'foobar_.csv_.csv.gz')[0]
'foobar_.csv_'
|
Correct way to edit dictionary value python
Question: I have written the following code in two different ways. I am trying to find
the "correct pythonic" way of doing it. I will explain the reasons for both.
First way, EAFP. This one uses pythons EAFP priciple, but causes some code
duplication.
try:
my_dict['foo']['bar'] = some_var
except KeyError:
my_dict['foo'] = {}
my_dict['foo']['bar'] = some_var
Second way, LBYL. LBYL is not exactly considered pythonic, but it removes the
code duplication.
if 'foo' not in my_dict:
my_dict['foo'] = {}
my_dict['foo']['bar'] = some_var
Which way would be considered best? Or is there a better way?
Answer: I would say a seasoned Python developer would either use
[dict.setdefault](https://docs.python.org/2/library/stdtypes.html#dict.setdefault)
or
[collections.defaultdict](https://docs.python.org/2/library/collections.html#collections.defaultdict)
my_dict.setdefault('foo', {})['bar'] = some_var
or
from collection import defaultdict
my_dict = defaultdict(dict)
my_dict['foo']['bar'] = some_var
Also for the sake of completeness, I will introduce you to a recursive
`defaultdict` pattern, which allows for dictionaries with infinite depth
without any key error
>>> from collections import defaultdict
>>> def tree(): return defaultdict(tree)
>>> my_dict = tree()
>>> my_dict['foo']['bar']['spam']['egg'] = 0
>>> my_dict
defaultdict(<function tree at 0x026FFDB0>, {'foo': defaultdict(<function tree at 0x026FFDB0>, {'bar': defaultdict(<function tree at 0x026FFDB0>, {'spam': defaultdict(<function tree at 0x026FFDB0>, {'egg': 0})})})})
|
Fetch 1M records in orientdb: why is it 6x slower than bare SQL+MySQL
Question: For some graph algorithm I need to fetch a lot of records from a database to
memory (~ 1M records). I want this to be done fast and I want the records to
be objects (that is: I want ORM). To crudely benchmark different solutions I
created a simple problem of one table with 1M Foo objects like I did here:
[Why is SQLAlchemy 10x slower than
SQL?](http://stackoverflow.com/questions/23185319/why-is-
sqlalchemy-10x-slower-than-sql) .
One can see that fetching them using bare SQL is extremely fast; also
converting the records to objects using a simple for-loop is fast. Both
execute in around 2-3 seconds. However using ORM's like SQLAlchemy and
Hibernate, this takes 20-30 seconds: a lot slower if you ask me, and this is
just a simple example without relations and joins.
SQLAlchemy gives itself the feature "Mature, High Performing Architecture,"
(<http://www.sqlalchemy.org/features.html>). Similarly for Hibernate "High
Performance" (<http://hibernate.org/orm/>). In a way both are right, because
they allow for very generic object oriented data models to be mapped back and
forth to a MySQL database. On the other hand they are awfully wrong, since
they are 10x slower than just SQL and native code. Personally I think they
could do better benchmarks to show this, that is, a benchmark comparing with
native SQL + java or python. But that is not the problem at hand.
Of course, I don't want SQL + native code, as it is hard to maintain. So I was
wondering why there does not exist something like an object oriented database,
which handles the database->object mapping native. Someone suggested OrientDB,
hence I tried it. The API is quite nice: when you have your getters and
setters right, the object is insertable and selectable.
But I want more than just API-sweetness, so I tried the 1M example:
import java.io.Serializable;
public class Foo implements Serializable {
public Foo() {}
public Foo(int a, int b, int c) { this.a=a; this.b=b; this.c=c; }
public int a,b,c;
public int getA() { return a; }
public void setA(int a) { this.a=a; }
public int getB() { return b; }
public void setB(int b) { this.b=b; }
public int getC() { return c; }
public void setC(int c) { this.c=c; }
}
import com.orientechnologies.orient.object.db.OObjectDatabaseTx;
public class Main {
public static void insert() throws Exception {
OObjectDatabaseTx db = new OObjectDatabaseTx ("plocal:/opt/orientdb-community-1.7.6/databases/test").open("admin", "admin");
db.getEntityManager().registerEntityClass(Foo.class);
int N=1000000;
long time = System.currentTimeMillis();
for(int i=0; i<N; i++) {
Foo foo = new Foo(i, i*i, i+i*i);
db.save(foo);
}
db.close();
System.out.println(System.currentTimeMillis() - time);
}
public static void fetch() {
OObjectDatabaseTx db = new OObjectDatabaseTx ("plocal:/opt/orientdb-community-1.7.6/databases/test").open("admin", "admin");
db.getEntityManager().registerEntityClass(Foo.class);
long time = System.currentTimeMillis();
for (Foo f : db.browseClass(Foo.class).setFetchPlan("*:-1")) {
if(f.getA() == 345234) System.out.println(f.getB());
}
System.out.println("Fetching all Foo records took: " + (System.currentTimeMillis() - time) + " ms");
db.close();
}
public static void main(String[] args) throws Exception {
//insert();
fetch();
}
}
Fetching 1M Foo's using **OrientDB** takes approximately **18 seconds**. The
for-loop with the getA() is to force the object fields to be actually loaded
into memory, as I noticed that by default they are fetched lazily. I guess
this may also be the reason fetching the Foo's is slow, because it has db-
access each iteration instead of db-access once when it fetches everything
(including the fields).
I tried to fix that using setFetchPlan("*:-1"), I figured it may also apply on
fields, but that did not seem to work.
**Question:** Is there a way to do this fast, preferably in the 2-3 seconds
range? Why does this take 18 seconds, whilst the bare SQL version uses 3
seconds?
**Addition:** Using a ODatabaseDocumentTX like @frens-jan-rumph suggested only
gave ma a speedup of approximately 5, but of approximatelt 2. Adjusting the
following code gave me a running time of approximately 9 seconds. This is
still 3 times slower than raw sql whilst no conversion to Foo's was executed.
Almost all time goes to the for-loop.
public static void fetch() {
ODatabaseDocumentTx db = new ODatabaseDocumentTx ("plocal:/opt/orientdb-community-1.7.6/databases/pits2").open("admin", "admin");
long time = System.currentTimeMillis();
ORecordIteratorClass<ODocument> it = db.browseClass("Foo");
it.setFetchPlan("*:0");
System.out.println("Fetching all Foo records took: " + (System.currentTimeMillis() - time) + " ms");
time = System.currentTimeMillis();
for (ODocument f : it) {
//if((int)f.field("a") == 345234) System.out.println(f.field("b"));
}
System.out.println("Iterating all Foo records took: " + (System.currentTimeMillis() - time) + " ms");
db.close();
}
Answer: The answer lies in convenience.
During an interview, when I asked a candidate what they thought of LINQ (C# I
know, but pertinent to your question), they quite rightly answered that it was
a sacrifice of performance, over convenience.
A hand-written SQL statement (whether or not it calls a stored procedure) is
_always_ going to be faster than using an ORM that auto-magically converts the
results of the query in to nice, easy-to-use POCOs.
That said, the difference should _not be that great_ as you have experienced.
Yes, there is overhead in doing it the auto-magical way, but it shouldn't be
that great. I do have experience here, and within C# I have had to use special
reflection classes to reduce the time it takes to do this auto-magical
mapping.
With large swabs of data, I would expect an initial slow-down from an ORM, but
then it would be negligible. 3 seconds to 18 seconds is _huge_.
|
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