Source code for textattack.constraints.pre_transformation.input_column_modification
"""
Input Column Modification
--------------------------
"""
from textattack.constraints import PreTransformationConstraint
[docs]class InputColumnModification(PreTransformationConstraint):
"""A constraint disallowing the modification of words within a specific
input column.
For example, can prevent modification of 'premise' during
entailment.
"""
def __init__(self, matching_column_labels, columns_to_ignore):
self.matching_column_labels = matching_column_labels
self.columns_to_ignore = columns_to_ignore
def _get_modifiable_indices(self, current_text):
"""Returns the word indices in current_text which are able to be
deleted.
If ``current_text.column_labels`` doesn't match
``self.matching_column_labels``, do nothing, and allow all words
to be modified.
If it does match, only allow words to be modified if they are not
in columns from ``columns_to_ignore``.
"""
if current_text.column_labels != self.matching_column_labels:
return set(range(len(current_text.words)))
idx = 0
indices_to_modify = set()
for column, words in zip(
current_text.column_labels, current_text.words_per_input
):
num_words = len(words)
if column not in self.columns_to_ignore:
indices_to_modify |= set(range(idx, idx + num_words))
idx += num_words
return indices_to_modify