File size: 23,192 Bytes
8777447 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 |
# Natural Language Toolkit: Text Trees
#
# Copyright (C) 2001-2023 NLTK Project
# Author: Edward Loper <[email protected]>
# Steven Bird <[email protected]>
# Peter Ljunglöf <[email protected]>
# Tom Aarsen <>
# URL: <https://www.nltk.org/>
# For license information, see LICENSE.TXT
import warnings
from abc import ABCMeta, abstractmethod
from nltk.tree.tree import Tree
from nltk.util import slice_bounds
######################################################################
## Parented trees
######################################################################
class AbstractParentedTree(Tree, metaclass=ABCMeta):
"""
An abstract base class for a ``Tree`` that automatically maintains
pointers to parent nodes. These parent pointers are updated
whenever any change is made to a tree's structure. Two subclasses
are currently defined:
- ``ParentedTree`` is used for tree structures where each subtree
has at most one parent. This class should be used in cases
where there is no"sharing" of subtrees.
- ``MultiParentedTree`` is used for tree structures where a
subtree may have zero or more parents. This class should be
used in cases where subtrees may be shared.
Subclassing
===========
The ``AbstractParentedTree`` class redefines all operations that
modify a tree's structure to call two methods, which are used by
subclasses to update parent information:
- ``_setparent()`` is called whenever a new child is added.
- ``_delparent()`` is called whenever a child is removed.
"""
def __init__(self, node, children=None):
super().__init__(node, children)
# If children is None, the tree is read from node, and
# all parents will be set during parsing.
if children is not None:
# Otherwise we have to set the parent of the children.
# Iterate over self, and *not* children, because children
# might be an iterator.
for i, child in enumerate(self):
if isinstance(child, Tree):
self._setparent(child, i, dry_run=True)
for i, child in enumerate(self):
if isinstance(child, Tree):
self._setparent(child, i)
# ////////////////////////////////////////////////////////////
# Parent management
# ////////////////////////////////////////////////////////////
@abstractmethod
def _setparent(self, child, index, dry_run=False):
"""
Update the parent pointer of ``child`` to point to ``self``. This
method is only called if the type of ``child`` is ``Tree``;
i.e., it is not called when adding a leaf to a tree. This method
is always called before the child is actually added to the
child list of ``self``.
:type child: Tree
:type index: int
:param index: The index of ``child`` in ``self``.
:raise TypeError: If ``child`` is a tree with an impropriate
type. Typically, if ``child`` is a tree, then its type needs
to match the type of ``self``. This prevents mixing of
different tree types (single-parented, multi-parented, and
non-parented).
:param dry_run: If true, the don't actually set the child's
parent pointer; just check for any error conditions, and
raise an exception if one is found.
"""
@abstractmethod
def _delparent(self, child, index):
"""
Update the parent pointer of ``child`` to not point to self. This
method is only called if the type of ``child`` is ``Tree``; i.e., it
is not called when removing a leaf from a tree. This method
is always called before the child is actually removed from the
child list of ``self``.
:type child: Tree
:type index: int
:param index: The index of ``child`` in ``self``.
"""
# ////////////////////////////////////////////////////////////
# Methods that add/remove children
# ////////////////////////////////////////////////////////////
# Every method that adds or removes a child must make
# appropriate calls to _setparent() and _delparent().
def __delitem__(self, index):
# del ptree[start:stop]
if isinstance(index, slice):
start, stop, step = slice_bounds(self, index, allow_step=True)
# Clear all the children pointers.
for i in range(start, stop, step):
if isinstance(self[i], Tree):
self._delparent(self[i], i)
# Delete the children from our child list.
super().__delitem__(index)
# del ptree[i]
elif isinstance(index, int):
if index < 0:
index += len(self)
if index < 0:
raise IndexError("index out of range")
# Clear the child's parent pointer.
if isinstance(self[index], Tree):
self._delparent(self[index], index)
# Remove the child from our child list.
super().__delitem__(index)
elif isinstance(index, (list, tuple)):
# del ptree[()]
if len(index) == 0:
raise IndexError("The tree position () may not be deleted.")
# del ptree[(i,)]
elif len(index) == 1:
del self[index[0]]
# del ptree[i1, i2, i3]
else:
del self[index[0]][index[1:]]
else:
raise TypeError(
"%s indices must be integers, not %s"
% (type(self).__name__, type(index).__name__)
)
def __setitem__(self, index, value):
# ptree[start:stop] = value
if isinstance(index, slice):
start, stop, step = slice_bounds(self, index, allow_step=True)
# make a copy of value, in case it's an iterator
if not isinstance(value, (list, tuple)):
value = list(value)
# Check for any error conditions, so we can avoid ending
# up in an inconsistent state if an error does occur.
for i, child in enumerate(value):
if isinstance(child, Tree):
self._setparent(child, start + i * step, dry_run=True)
# clear the child pointers of all parents we're removing
for i in range(start, stop, step):
if isinstance(self[i], Tree):
self._delparent(self[i], i)
# set the child pointers of the new children. We do this
# after clearing *all* child pointers, in case we're e.g.
# reversing the elements in a tree.
for i, child in enumerate(value):
if isinstance(child, Tree):
self._setparent(child, start + i * step)
# finally, update the content of the child list itself.
super().__setitem__(index, value)
# ptree[i] = value
elif isinstance(index, int):
if index < 0:
index += len(self)
if index < 0:
raise IndexError("index out of range")
# if the value is not changing, do nothing.
if value is self[index]:
return
# Set the new child's parent pointer.
if isinstance(value, Tree):
self._setparent(value, index)
# Remove the old child's parent pointer
if isinstance(self[index], Tree):
self._delparent(self[index], index)
# Update our child list.
super().__setitem__(index, value)
elif isinstance(index, (list, tuple)):
# ptree[()] = value
if len(index) == 0:
raise IndexError("The tree position () may not be assigned to.")
# ptree[(i,)] = value
elif len(index) == 1:
self[index[0]] = value
# ptree[i1, i2, i3] = value
else:
self[index[0]][index[1:]] = value
else:
raise TypeError(
"%s indices must be integers, not %s"
% (type(self).__name__, type(index).__name__)
)
def append(self, child):
if isinstance(child, Tree):
self._setparent(child, len(self))
super().append(child)
def extend(self, children):
for child in children:
if isinstance(child, Tree):
self._setparent(child, len(self))
super().append(child)
def insert(self, index, child):
# Handle negative indexes. Note that if index < -len(self),
# we do *not* raise an IndexError, unlike __getitem__. This
# is done for consistency with list.__getitem__ and list.index.
if index < 0:
index += len(self)
if index < 0:
index = 0
# Set the child's parent, and update our child list.
if isinstance(child, Tree):
self._setparent(child, index)
super().insert(index, child)
def pop(self, index=-1):
if index < 0:
index += len(self)
if index < 0:
raise IndexError("index out of range")
if isinstance(self[index], Tree):
self._delparent(self[index], index)
return super().pop(index)
# n.b.: like `list`, this is done by equality, not identity!
# To remove a specific child, use del ptree[i].
def remove(self, child):
index = self.index(child)
if isinstance(self[index], Tree):
self._delparent(self[index], index)
super().remove(child)
# We need to implement __getslice__ and friends, even though
# they're deprecated, because otherwise list.__getslice__ will get
# called (since we're subclassing from list). Just delegate to
# __getitem__ etc., but use max(0, start) and max(0, stop) because
# because negative indices are already handled *before*
# __getslice__ is called; and we don't want to double-count them.
if hasattr(list, "__getslice__"):
def __getslice__(self, start, stop):
return self.__getitem__(slice(max(0, start), max(0, stop)))
def __delslice__(self, start, stop):
return self.__delitem__(slice(max(0, start), max(0, stop)))
def __setslice__(self, start, stop, value):
return self.__setitem__(slice(max(0, start), max(0, stop)), value)
def __getnewargs__(self):
"""Method used by the pickle module when un-pickling.
This method provides the arguments passed to ``__new__``
upon un-pickling. Without this method, ParentedTree instances
cannot be pickled and unpickled in Python 3.7+ onwards.
:return: Tuple of arguments for ``__new__``, i.e. the label
and the children of this node.
:rtype: Tuple[Any, List[AbstractParentedTree]]
"""
return (self._label, list(self))
class ParentedTree(AbstractParentedTree):
"""
A ``Tree`` that automatically maintains parent pointers for
single-parented trees. The following are methods for querying
the structure of a parented tree: ``parent``, ``parent_index``,
``left_sibling``, ``right_sibling``, ``root``, ``treeposition``.
Each ``ParentedTree`` may have at most one parent. In
particular, subtrees may not be shared. Any attempt to reuse a
single ``ParentedTree`` as a child of more than one parent (or
as multiple children of the same parent) will cause a
``ValueError`` exception to be raised.
``ParentedTrees`` should never be used in the same tree as ``Trees``
or ``MultiParentedTrees``. Mixing tree implementations may result
in incorrect parent pointers and in ``TypeError`` exceptions.
"""
def __init__(self, node, children=None):
self._parent = None
"""The parent of this Tree, or None if it has no parent."""
super().__init__(node, children)
if children is None:
# If children is None, the tree is read from node.
# After parsing, the parent of the immediate children
# will point to an intermediate tree, not self.
# We fix this by brute force:
for i, child in enumerate(self):
if isinstance(child, Tree):
child._parent = None
self._setparent(child, i)
def _frozen_class(self):
from nltk.tree.immutable import ImmutableParentedTree
return ImmutableParentedTree
def copy(self, deep=False):
if not deep:
warnings.warn(
f"{self.__class__.__name__} objects do not support shallow copies. Defaulting to a deep copy."
)
return super().copy(deep=True)
# /////////////////////////////////////////////////////////////////
# Methods
# /////////////////////////////////////////////////////////////////
def parent(self):
"""The parent of this tree, or None if it has no parent."""
return self._parent
def parent_index(self):
"""
The index of this tree in its parent. I.e.,
``ptree.parent()[ptree.parent_index()] is ptree``. Note that
``ptree.parent_index()`` is not necessarily equal to
``ptree.parent.index(ptree)``, since the ``index()`` method
returns the first child that is equal to its argument.
"""
if self._parent is None:
return None
for i, child in enumerate(self._parent):
if child is self:
return i
assert False, "expected to find self in self._parent!"
def left_sibling(self):
"""The left sibling of this tree, or None if it has none."""
parent_index = self.parent_index()
if self._parent and parent_index > 0:
return self._parent[parent_index - 1]
return None # no left sibling
def right_sibling(self):
"""The right sibling of this tree, or None if it has none."""
parent_index = self.parent_index()
if self._parent and parent_index < (len(self._parent) - 1):
return self._parent[parent_index + 1]
return None # no right sibling
def root(self):
"""
The root of this tree. I.e., the unique ancestor of this tree
whose parent is None. If ``ptree.parent()`` is None, then
``ptree`` is its own root.
"""
root = self
while root.parent() is not None:
root = root.parent()
return root
def treeposition(self):
"""
The tree position of this tree, relative to the root of the
tree. I.e., ``ptree.root[ptree.treeposition] is ptree``.
"""
if self.parent() is None:
return ()
else:
return self.parent().treeposition() + (self.parent_index(),)
# /////////////////////////////////////////////////////////////////
# Parent Management
# /////////////////////////////////////////////////////////////////
def _delparent(self, child, index):
# Sanity checks
assert isinstance(child, ParentedTree)
assert self[index] is child
assert child._parent is self
# Delete child's parent pointer.
child._parent = None
def _setparent(self, child, index, dry_run=False):
# If the child's type is incorrect, then complain.
if not isinstance(child, ParentedTree):
raise TypeError("Can not insert a non-ParentedTree into a ParentedTree")
# If child already has a parent, then complain.
if hasattr(child, "_parent") and child._parent is not None:
raise ValueError("Can not insert a subtree that already has a parent.")
# Set child's parent pointer & index.
if not dry_run:
child._parent = self
class MultiParentedTree(AbstractParentedTree):
"""
A ``Tree`` that automatically maintains parent pointers for
multi-parented trees. The following are methods for querying the
structure of a multi-parented tree: ``parents()``, ``parent_indices()``,
``left_siblings()``, ``right_siblings()``, ``roots``, ``treepositions``.
Each ``MultiParentedTree`` may have zero or more parents. In
particular, subtrees may be shared. If a single
``MultiParentedTree`` is used as multiple children of the same
parent, then that parent will appear multiple times in its
``parents()`` method.
``MultiParentedTrees`` should never be used in the same tree as
``Trees`` or ``ParentedTrees``. Mixing tree implementations may
result in incorrect parent pointers and in ``TypeError`` exceptions.
"""
def __init__(self, node, children=None):
self._parents = []
"""A list of this tree's parents. This list should not
contain duplicates, even if a parent contains this tree
multiple times."""
super().__init__(node, children)
if children is None:
# If children is None, the tree is read from node.
# After parsing, the parent(s) of the immediate children
# will point to an intermediate tree, not self.
# We fix this by brute force:
for i, child in enumerate(self):
if isinstance(child, Tree):
child._parents = []
self._setparent(child, i)
def _frozen_class(self):
from nltk.tree.immutable import ImmutableMultiParentedTree
return ImmutableMultiParentedTree
# /////////////////////////////////////////////////////////////////
# Methods
# /////////////////////////////////////////////////////////////////
def parents(self):
"""
The set of parents of this tree. If this tree has no parents,
then ``parents`` is the empty set. To check if a tree is used
as multiple children of the same parent, use the
``parent_indices()`` method.
:type: list(MultiParentedTree)
"""
return list(self._parents)
def left_siblings(self):
"""
A list of all left siblings of this tree, in any of its parent
trees. A tree may be its own left sibling if it is used as
multiple contiguous children of the same parent. A tree may
appear multiple times in this list if it is the left sibling
of this tree with respect to multiple parents.
:type: list(MultiParentedTree)
"""
return [
parent[index - 1]
for (parent, index) in self._get_parent_indices()
if index > 0
]
def right_siblings(self):
"""
A list of all right siblings of this tree, in any of its parent
trees. A tree may be its own right sibling if it is used as
multiple contiguous children of the same parent. A tree may
appear multiple times in this list if it is the right sibling
of this tree with respect to multiple parents.
:type: list(MultiParentedTree)
"""
return [
parent[index + 1]
for (parent, index) in self._get_parent_indices()
if index < (len(parent) - 1)
]
def _get_parent_indices(self):
return [
(parent, index)
for parent in self._parents
for index, child in enumerate(parent)
if child is self
]
def roots(self):
"""
The set of all roots of this tree. This set is formed by
tracing all possible parent paths until trees with no parents
are found.
:type: list(MultiParentedTree)
"""
return list(self._get_roots_helper({}).values())
def _get_roots_helper(self, result):
if self._parents:
for parent in self._parents:
parent._get_roots_helper(result)
else:
result[id(self)] = self
return result
def parent_indices(self, parent):
"""
Return a list of the indices where this tree occurs as a child
of ``parent``. If this child does not occur as a child of
``parent``, then the empty list is returned. The following is
always true::
for parent_index in ptree.parent_indices(parent):
parent[parent_index] is ptree
"""
if parent not in self._parents:
return []
else:
return [index for (index, child) in enumerate(parent) if child is self]
def treepositions(self, root):
"""
Return a list of all tree positions that can be used to reach
this multi-parented tree starting from ``root``. I.e., the
following is always true::
for treepos in ptree.treepositions(root):
root[treepos] is ptree
"""
if self is root:
return [()]
else:
return [
treepos + (index,)
for parent in self._parents
for treepos in parent.treepositions(root)
for (index, child) in enumerate(parent)
if child is self
]
# /////////////////////////////////////////////////////////////////
# Parent Management
# /////////////////////////////////////////////////////////////////
def _delparent(self, child, index):
# Sanity checks
assert isinstance(child, MultiParentedTree)
assert self[index] is child
assert len([p for p in child._parents if p is self]) == 1
# If the only copy of child in self is at index, then delete
# self from child's parent list.
for i, c in enumerate(self):
if c is child and i != index:
break
else:
child._parents.remove(self)
def _setparent(self, child, index, dry_run=False):
# If the child's type is incorrect, then complain.
if not isinstance(child, MultiParentedTree):
raise TypeError(
"Can not insert a non-MultiParentedTree into a MultiParentedTree"
)
# Add self as a parent pointer if it's not already listed.
if not dry_run:
for parent in child._parents:
if parent is self:
break
else:
child._parents.append(self)
__all__ = [
"ParentedTree",
"MultiParentedTree",
]
|