Source code for pytext.fields.char_field

#!/usr/bin/env python3
# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
import copy
from collections import Counter
from typing import List

import torch
from pytext.common.constants import VocabMeta
from pytext.utils.data_utils import no_tokenize
from torchtext import data as textdata, vocab

from .field import VocabUsingField


[docs]class CharFeatureField(VocabUsingField): dummy_model_input = torch.tensor( [[[1, 1, 1]], [[1, 1, 1]]], dtype=torch.long, device="cpu" ) def __init__( self, pad_token=VocabMeta.PAD_TOKEN, unk_token=VocabMeta.UNK_TOKEN, batch_first=True, **kwargs ): super().__init__( sequential=True, # Otherwise pad is set to None in textdata.Field batch_first=batch_first, tokenize=no_tokenize, use_vocab=True, pad_token=pad_token, unk_token=unk_token, )
[docs] def build_vocab(self, *args, **kwargs): sources = [] for arg in args: if isinstance(arg, textdata.Dataset): sources += [ getattr(arg, name) for name, field in arg.fields.items() if field is self ] else: sources.append(arg) counter = Counter() for data in sources: # data is the return value of preprocess(). for sentence in data: for word_chars in sentence: # update treats word as an iterable, so this will add all # the characters from the word, not the word itself. counter.update(word_chars) specials = [self.unk_token, self.pad_token] self.vocab = vocab.Vocab(counter, specials=specials, **kwargs)
[docs] def pad(self, minibatch: List[List[List[str]]]) -> List[List[List[str]]]: """ Example of minibatch: :: [[['p', 'l', 'a', 'y', '<PAD>', '<PAD>'], ['t', 'h', 'a', 't', '<PAD>', '<PAD>'], ['t', 'r', 'a', 'c', 'k', '<PAD>'], ['o', 'n', '<PAD>', '<PAD>', '<PAD>', '<PAD>'], ['r', 'e', 'p', 'e', 'a', 't'] ], ... ] """ # If we change the same minibatch object then the underlying data # will get corrupted. Hence deep copy the minibatch object. padded_minibatch = copy.deepcopy(minibatch) max_sentence_length, max_word_length = 0, 0 for sent in minibatch: max_sentence_length = max(max_sentence_length, len(sent)) for word in sent: max_word_length = max(max_word_length, len(word)) for i, sentence in enumerate(minibatch): for j, word in enumerate(sentence): char_padding = [self.pad_token] * (max_word_length - len(word)) padded_minibatch[i][j].extend(char_padding) if len(sentence) < max_sentence_length: for _ in range(max_sentence_length - len(sentence)): char_padding = [self.pad_token] * max_word_length padded_minibatch[i].append(char_padding) return padded_minibatch
[docs] def numericalize(self, batch, device=None): batch_char_ids = [] for sentence in batch: sentence_char_ids = super().numericalize(sentence, device=device) batch_char_ids.append(sentence_char_ids) return torch.stack(batch_char_ids, dim=0)