| """ | |
| Word Swap | |
| ------------------------------- | |
| Word swap transformations act by replacing some words in the input. Subclasses can implement the abstract ``WordSwap`` class by overriding ``self._get_replacement_words`` | |
| """ | |
| import random | |
| import string | |
| from textattack.transformations import Transformation | |
| class WordSwap(Transformation): | |
| """An abstract class that takes a sentence and transforms it by replacing | |
| some of its words. | |
| letters_to_insert (string): letters allowed for insertion into words | |
| (used by some char-based transformations) | |
| """ | |
| def __init__(self, letters_to_insert=None): | |
| self.letters_to_insert = letters_to_insert | |
| if not self.letters_to_insert: | |
| self.letters_to_insert = string.ascii_letters | |
| def _get_replacement_words(self, word): | |
| """Returns a set of replacements given an input word. Must be overriden | |
| by specific word swap transformations. | |
| Args: | |
| word: The input word to find replacements for. | |
| """ | |
| raise NotImplementedError() | |
| def _get_random_letter(self): | |
| """Helper function that returns a random single letter from the English | |
| alphabet that could be lowercase or uppercase.""" | |
| return random.choice(self.letters_to_insert) | |
| def _get_transformations(self, current_text, indices_to_modify): | |
| words = current_text.words | |
| transformed_texts = [] | |
| for i in indices_to_modify: | |
| word_to_replace = words[i] | |
| replacement_words = self._get_replacement_words(word_to_replace) | |
| transformed_texts_idx = [] | |
| for r in replacement_words: | |
| if r == word_to_replace: | |
| continue | |
| transformed_texts_idx.append(current_text.replace_word_at_index(i, r)) | |
| transformed_texts.extend(transformed_texts_idx) | |
| return transformed_texts | |