Source code for textattack.constraints.overlap.max_words_perturbed


Max Perturb Words Constraints


import math

from textattack.constraints import Constraint

[docs]class MaxWordsPerturbed(Constraint): """A constraint representing a maximum allowed perturbed words. Args: max_num_words (:obj:`int`, optional): Maximum number of perturbed words allowed. max_percent (:obj: `float`, optional): Maximum percentage of words allowed to be perturbed. compare_against_original (bool): If `True`, compare new `x_adv` against the original `x`. Otherwise, compare it against the previous `x_adv`. """ def __init__( self, max_num_words=None, max_percent=None, compare_against_original=True ): super().__init__(compare_against_original) if not compare_against_original: raise ValueError( "Cannot apply constraint MaxWordsPerturbed with `compare_against_original=False`" ) if (max_num_words is None) and (max_percent is None): raise ValueError("must set either `max_percent` or `max_num_words`") if max_percent and not (0 <= max_percent <= 1): raise ValueError("max perc must be between 0 and 1") self.max_num_words = max_num_words self.max_percent = max_percent def _check_constraint(self, transformed_text, reference_text): num_words_diff = len(transformed_text.all_words_diff(reference_text)) if self.max_percent: min_num_words = min(len(transformed_text.words), len(reference_text.words)) max_words_perturbed = math.ceil(min_num_words * (self.max_percent)) max_percent_met = num_words_diff <= max_words_perturbed else: max_percent_met = True if self.max_num_words: max_num_words_met = num_words_diff <= self.max_num_words else: max_num_words_met = True return max_percent_met and max_num_words_met
[docs] def extra_repr_keys(self): metric = [] if self.max_percent is not None: metric.append("max_percent") if self.max_num_words is not None: metric.append("max_num_words") return metric + super().extra_repr_keys()