Source code for textattack.transformations.transformation

Transformation Abstract Class


from abc import ABC, abstractmethod

from textattack.shared.utils import ReprMixin

[docs]class Transformation(ReprMixin, ABC): """An abstract class for transforming a sequence of text to produce a potential adversarial example.""" def __call__( self, current_text, pre_transformation_constraints=[], indices_to_modify=None, shifted_idxs=False, return_indices=False, ): """Returns a list of all possible transformations for ``current_text``. Applies the ``pre_transformation_constraints`` then calls ``_get_transformations``. Args: current_text: The ``AttackedText`` to transform. pre_transformation_constraints: The ``PreTransformationConstraint`` to apply before beginning the transformation. indices_to_modify: Which word indices should be modified as dictated by the ``SearchMethod``. shifted_idxs (bool): Whether indices could have been shifted from their original position in the text. return_indices (bool): Whether the function returns indices_to_modify instead of the transformed_texts. """ if indices_to_modify is None: indices_to_modify = set(range(len(current_text.words))) # If we are modifying all indices, we don't care if some of the indices might have been shifted. shifted_idxs = False else: indices_to_modify = set(indices_to_modify) if shifted_idxs: indices_to_modify = set( current_text.convert_from_original_idxs(indices_to_modify) ) for constraint in pre_transformation_constraints: indices_to_modify = indices_to_modify & constraint(current_text, self) if return_indices: return indices_to_modify transformed_texts = self._get_transformations(current_text, indices_to_modify) for text in transformed_texts: text.attack_attrs["last_transformation"] = self return transformed_texts @abstractmethod def _get_transformations(self, current_text, indices_to_modify): """Returns a list of all possible transformations for ``current_text``, only modifying ``indices_to_modify``. Must be overridden by specific transformations. Args: current_text: The ``AttackedText`` to transform. indicies_to_modify: Which word indices can be modified. """ raise NotImplementedError() @property def deterministic(self): return True