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# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import unicodedata
import sacrebleu as sb
from fairseq.dataclass import ChoiceEnum
SACREBLEU_V2_ABOVE = int(sb.__version__[0]) >= 2
class EvaluationTokenizer(object):
"""A generic evaluation-time tokenizer, which leverages built-in tokenizers
in sacreBLEU (https://github.com/mjpost/sacrebleu). It additionally provides
lowercasing, punctuation removal and character tokenization, which are
applied after sacreBLEU tokenization.
Args:
tokenizer_type (str): the type of sacreBLEU tokenizer to apply.
lowercase (bool): lowercase the text.
punctuation_removal (bool): remove punctuation (based on unicode
category) from text.
character_tokenization (bool): tokenize the text to characters.
"""
SPACE = chr(32)
SPACE_ESCAPE = chr(9601)
_ALL_TOKENIZER_TYPES = (
sb.BLEU.TOKENIZERS
if SACREBLEU_V2_ABOVE
else ["none", "13a", "intl", "zh", "ja-mecab"]
)
ALL_TOKENIZER_TYPES = ChoiceEnum(_ALL_TOKENIZER_TYPES)
def __init__(
self,
tokenizer_type: str = "13a",
lowercase: bool = False,
punctuation_removal: bool = False,
character_tokenization: bool = False,
):
assert (
tokenizer_type in self._ALL_TOKENIZER_TYPES
), f"{tokenizer_type}, {self._ALL_TOKENIZER_TYPES}"
self.lowercase = lowercase
self.punctuation_removal = punctuation_removal
self.character_tokenization = character_tokenization
if SACREBLEU_V2_ABOVE:
self.tokenizer = sb.BLEU(tokenize=str(tokenizer_type)).tokenizer
else:
self.tokenizer = sb.tokenizers.TOKENIZERS[tokenizer_type]()
@classmethod
def remove_punctuation(cls, sent: str):
"""Remove punctuation based on Unicode category."""
return cls.SPACE.join(
t
for t in sent.split(cls.SPACE)
if not all(unicodedata.category(c)[0] == "P" for c in t)
)
def tokenize(self, sent: str):
tokenized = self.tokenizer(sent)
if self.punctuation_removal:
tokenized = self.remove_punctuation(tokenized)
if self.character_tokenization:
tokenized = self.SPACE.join(
list(tokenized.replace(self.SPACE, self.SPACE_ESCAPE))
)
if self.lowercase:
tokenized = tokenized.lower()
return tokenized
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