nemo/collections/common/tokenizers/en_ja_tokenizers.py

# Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import re
from typing import List

try:
    import ipadic
    import MeCab

    HAVE_MECAB = True
    HAVE_IPADIC = True
except (ImportError, ModuleNotFoundError):
    HAVE_MECAB = False
    HAVE_IPADIC = False


class EnJaProcessor:
    """
    Tokenizer, Detokenizer and Normalizer utilities for Japanese & English
    Args:
        lang_id: One of ['en', 'ja'].
    """

    def __init__(self, lang_id: str):
        from sacremoses import MosesDetokenizer, MosesPunctNormalizer, MosesTokenizer

        self.lang_id = lang_id
        self.moses_tokenizer = MosesTokenizer(lang=lang_id)
        self.moses_detokenizer = MosesDetokenizer(lang=lang_id)
        self.normalizer = MosesPunctNormalizer(
            lang=lang_id, pre_replace_unicode_punct=True, post_remove_control_chars=True
        )

    def detokenize(self, tokens: List[str]) -> str:
        """
        Detokenizes a list of tokens
        Args:
            tokens: list of strings as tokens
        Returns:
            detokenized Japanese or English string
        """
        return self.moses_detokenizer.detokenize(tokens)

    def tokenize(self, text) -> str:
        """
        Tokenizes text using Moses. Returns a string of tokens.
        """
        tokens = self.moses_tokenizer.tokenize(text)
        return ' '.join(tokens)

    def normalize(self, text) -> str:
        # Normalization doesn't handle Japanese periods correctly;
        # '。'becomes '.'.
        if self.lang_id == 'en':
            return self.normalizer.normalize(text)
        else:
            return text


class JaMecabProcessor:
    """
    Tokenizer, Detokenizer and Normalizer utilities for Japanese MeCab & English
    """

    def __init__(self):
        if not HAVE_MECAB or not HAVE_IPADIC:
            raise ImportError("Please ensure that you have installed `MeCab` and `ipadic` to use JaMecabProcessor")

        self.mecab_tokenizer = MeCab.Tagger(ipadic.MECAB_ARGS + " -Owakati")

    def detokenize(self, text: List[str]) -> str:
        from pangu import spacing

        RE_WS_IN_FW = re.compile(
            r'([\u2018\u2019\u201c\u201d\u2e80-\u312f\u3200-\u32ff\u3400-\u4dbf\u4e00-\u9fff\uf900-\ufaff\uff00-\uffef])\s+(?=[\u2018\u2019\u201c\u201d\u2e80-\u312f\u3200-\u32ff\u3400-\u4dbf\u4e00-\u9fff\uf900-\ufaff\uff00-\uffef])'
        )

        detokenize = lambda s: spacing(RE_WS_IN_FW.sub(r'\1', s)).strip()
        return detokenize(' '.join(text))

    def tokenize(self, text) -> str:
        """
        Tokenizes text using Moses. Returns a string of tokens.
        """
        return self.mecab_tokenizer.parse(text).strip()

    def normalize(self, text) -> str:
        return text