Source code for transformers.tokenization_openai

# 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.
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"""Tokenization classes for OpenAI GPT."""
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import json
import logging
import os
import re
from io import open

from .tokenization_utils import PreTrainedTokenizer
from .tokenization_bert import BasicTokenizer

logger = logging.getLogger(__name__)

VOCAB_FILES_NAMES = {
    'vocab_file': 'vocab.json',
    'merges_file': 'merges.txt',
}

PRETRAINED_VOCAB_FILES_MAP = {
    'vocab_file':
    {
        'openai-gpt': "https://s3.amazonaws.com/models.huggingface.co/bert/openai-gpt-vocab.json",
    },
    'merges_file':
    {
        'openai-gpt': "https://s3.amazonaws.com/models.huggingface.co/bert/openai-gpt-merges.txt",
    },
}

PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES = {
    'openai-gpt': 512,
}

def get_pairs(word):
    """
    Return set of symbol pairs in a word.
    word is represented as tuple of symbols (symbols being variable-length strings)
    """
    pairs = set()
    prev_char = word[0]
    for char in word[1:]:
        pairs.add((prev_char, char))
        prev_char = char
    return pairs

def text_standardize(text):
    """
    fixes some issues the spacy tokenizer had on books corpus
    also does some whitespace standardization
    """
    text = text.replace('—', '-')
    text = text.replace('–', '-')
    text = text.replace('―', '-')
    text = text.replace('…', '...')
    text = text.replace('´', "'")
    text = re.sub(r'''(-+|~+|!+|"+|;+|\?+|\++|,+|\)+|\(+|\\+|\/+|\*+|\[+|\]+|}+|{+|\|+|_+)''', r' \1 ', text)
    text = re.sub(r'\s*\n\s*', ' \n ', text)
    text = re.sub(r'[^\S\n]+', ' ', text)
    return text.strip()

[docs]class OpenAIGPTTokenizer(PreTrainedTokenizer): """ BPE tokenizer. Peculiarities: - lower case all inputs - uses SpaCy tokenizer and ftfy for pre-BPE tokenization if they are installed, fallback to BERT's BasicTokenizer if not. """ vocab_files_names = VOCAB_FILES_NAMES pretrained_vocab_files_map = PRETRAINED_VOCAB_FILES_MAP max_model_input_sizes = PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES def __init__(self, vocab_file, merges_file, unk_token="<unk>", **kwargs): super(OpenAIGPTTokenizer, self).__init__(unk_token=unk_token, **kwargs) self.max_len_single_sentence = self.max_len # no default special tokens - you can update this value if you add special tokens self.max_len_sentences_pair = self.max_len # no default special tokens - you can update this value if you add special tokens try: import ftfy from spacy.lang.en import English _nlp = English() self.nlp = _nlp.Defaults.create_tokenizer(_nlp) self.fix_text = ftfy.fix_text except ImportError: logger.warning("ftfy or spacy is not installed using BERT BasicTokenizer instead of SpaCy & ftfy.") self.nlp = BasicTokenizer(do_lower_case=True) self.fix_text = None self.encoder = json.load(open(vocab_file, encoding="utf-8")) self.decoder = {v:k for k,v in self.encoder.items()} merges = open(merges_file, encoding='utf-8').read().split('\n')[1:-1] merges = [tuple(merge.split()) for merge in merges] self.bpe_ranks = dict(zip(merges, range(len(merges)))) self.cache = {} @property def vocab_size(self): return len(self.encoder) def bpe(self, token): word = tuple(token[:-1]) + (token[-1] + '</w>',) if token in self.cache: return self.cache[token] pairs = get_pairs(word) if not pairs: return token+'</w>' while True: bigram = min(pairs, key=lambda pair: self.bpe_ranks.get(pair, float('inf'))) if bigram not in self.bpe_ranks: break first, second = bigram new_word = [] i = 0 while i < len(word): try: j = word.index(first, i) new_word.extend(word[i:j]) i = j except: new_word.extend(word[i:]) break if word[i] == first and i < len(word)-1 and word[i+1] == second: new_word.append(first+second) i += 2 else: new_word.append(word[i]) i += 1 new_word = tuple(new_word) word = new_word if len(word) == 1: break else: pairs = get_pairs(word) word = ' '.join(word) if word == '\n </w>': word = '\n</w>' self.cache[token] = word return word def _tokenize(self, text): """ Tokenize a string. """ split_tokens = [] if self.fix_text is None: # Using BERT's BasicTokenizer text = self.nlp.tokenize(text) for token in text: split_tokens.extend([t for t in self.bpe(token).split(' ')]) else: # Using SpaCy & ftfy (original tokenization process of OpenAI GPT) text = self.nlp(text_standardize(self.fix_text(text))) for token in text: split_tokens.extend([t for t in self.bpe(token.text.lower()).split(' ')]) return split_tokens def _convert_token_to_id(self, token): """ Converts a token (str/unicode) in an id using the vocab. """ return self.encoder.get(token, self.encoder.get(self.unk_token)) def _convert_id_to_token(self, index): """Converts an id in a token (BPE) using the vocab.""" return self.decoder.get(index, self.unk_token)
[docs] def convert_tokens_to_string(self, tokens): """ Converts a sequence of tokens (string) in a single string. """ out_string = ''.join(tokens).replace('</w>', ' ').strip() return out_string
[docs] def save_vocabulary(self, save_directory): """Save the tokenizer vocabulary and merge files to a directory.""" if not os.path.isdir(save_directory): logger.error("Vocabulary path ({}) should be a directory".format(save_directory)) return vocab_file = os.path.join(save_directory, VOCAB_FILES_NAMES['vocab_file']) merge_file = os.path.join(save_directory, VOCAB_FILES_NAMES['merges_file']) with open(vocab_file, 'w', encoding='utf-8') as f: f.write(json.dumps(self.encoder, ensure_ascii=False)) index = 0 with open(merge_file, "w", encoding="utf-8") as writer: writer.write(u'#version: 0.2\n') for bpe_tokens, token_index in sorted(self.bpe_ranks.items(), key=lambda kv: kv[1]): if index != token_index: logger.warning("Saving vocabulary to {}: BPE merge indices are not consecutive." " Please check that the tokenizer is not corrupted!".format(merge_file)) index = token_index writer.write(' '.join(bpe_tokens) + u'\n') index += 1 return vocab_file, merge_file