app.py

import gradio as gr
import pymorphy3

morph = pymorphy3.MorphAnalyzer()
morph = pymorphy3.MorphAnalyzer(lang='ru')

def infinitive(word):
    p = morph.parse(str(word))[0]
    return p.normal_form

iface = gr.Interface(fn=infinitive, inputs="text", outputs="text")
iface.launch()