tokenization_gpt2.py

# coding=utf-8
# Copyright 2018 The Open AI Team Authors and The HuggingFace Inc. team.
#
# 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.
"""Tokenization classes for OpenAI GPT."""
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import json
from io import open
import sentencepiece as spm
import jieba

try:
    from functools import lru_cache
except ImportError:
    # Just a dummy decorator to get the checks to run on python2
    # because honestly I don't want to support a byte-level unicode BPE tokenizer on python 2 right now.
    def lru_cache():
        return lambda func: func

class GPT2Tokenizer(object):

    def __init__(self, vocab_file, model_file, max_len=None):
        self.max_len = max_len if max_len is not None else int(1e12)
        self.encoder = json.load(open(vocab_file))
        self.decoder = {v:k for k,v in self.encoder.items()}

        self.sp = spm.SentencePieceProcessor(model_file=model_file)
        self.translator = str.maketrans(" \n", "\u2582\u2583")

        self.eod_id = self.encoder['<eod>']

    @property
    def vocab_size(self):
        return len(self.encoder)

    def __len__(self):
        return len(self.encoder) + len(self.special_tokens)

    @property
    def eod(self):
        return self.eod_id

    def tokenize(self, text):
        """ Tokenize a string. """
        seg_list = [x.translate(self.translator) for x in jieba.cut(text, cut_all=False)]
        new_seg = " ".join(seg_list)
        return self.sp.encode(new_seg)

    def encode(self, text):
        res = self.tokenize(text)
        return res

    def decode(self, tokens):
        text = self.sp.decode(tokens)
        text = text.replace(' ', '').replace('\u2582', ' ').replace('\u2583', '\n')
        return text