|
| 1 | +from collections import Counter |
| 2 | + |
| 3 | +import numpy as np |
| 4 | +from torch.utils.data import Dataset |
| 5 | +import six |
| 6 | + |
| 7 | +import json |
| 8 | + |
| 9 | + |
| 10 | +class Vocabulary(object): |
| 11 | + """ |
| 12 | + An implementation that manages the interface between a token dataset and the |
| 13 | + machine learning algorithm. |
| 14 | + """ |
| 15 | + |
| 16 | + def __init__(self, use_unks=False, unk_token="<UNK>", |
| 17 | + use_mask=False, mask_token="<MASK>", use_start_end=False, |
| 18 | + start_token="<START>", end_token="<END>"): |
| 19 | + """ |
| 20 | + Args: |
| 21 | + use_unks (bool): The vocabulary will output UNK tokens for out of |
| 22 | + vocabulary items. |
| 23 | + [default=False] |
| 24 | + unk_token (str): The token used for unknown tokens. |
| 25 | + If `use_unks` is True, this will be added to the vocabulary. |
| 26 | + [default='<UNK>'] |
| 27 | + use_mask (bool): The vocabulary will reserve the 0th index for a mask token. |
| 28 | + This is used to handle variable lengths in sequence models. |
| 29 | + [default=False] |
| 30 | + mask_token (str): The token used for the mask. |
| 31 | + Note: mostly a placeholder; it's unlikely the token will be seen. |
| 32 | + [default='<MASK>'] |
| 33 | + use_start_end (bool): The vocabulary will reserve indices for two tokens |
| 34 | + that represent the start and end of a sequence. |
| 35 | + [default=False] |
| 36 | + start_token: The token used to indicate the start of a sequence. |
| 37 | + If `use_start_end` is True, this will be added to the vocabulary. |
| 38 | + [default='<START>'] |
| 39 | + end_token: The token used to indicate the end of a sequence |
| 40 | + If `use_start_end` is True, this will be added to the vocabulary. |
| 41 | + [default='<END>'] |
| 42 | + """ |
| 43 | + |
| 44 | + self._mapping = {} # str -> int |
| 45 | + self._flip = {} # int -> str; |
| 46 | + self._counts = Counter() # int -> int; count occurrences |
| 47 | + self._forced_unks = set() # force tokens to unk (e.g. if < 5 occurrences) |
| 48 | + self._i = 0 |
| 49 | + self._frozen = False |
| 50 | + self._frequency_threshold = -1 |
| 51 | + |
| 52 | + # mask token for use in masked recurrent networks |
| 53 | + # usually need to be the 0th index |
| 54 | + self.use_mask = use_mask |
| 55 | + self.mask_token = mask_token |
| 56 | + if self.use_mask: |
| 57 | + self.add(self.mask_token) |
| 58 | + |
| 59 | + # unk token for out of vocabulary tokens |
| 60 | + self.use_unks = use_unks |
| 61 | + self.unk_token = unk_token |
| 62 | + if self.use_unks: |
| 63 | + self.add(self.unk_token) |
| 64 | + |
| 65 | + # start token for sequence models |
| 66 | + self.use_start_end = use_start_end |
| 67 | + self.start_token = start_token |
| 68 | + self.end_token = end_token |
| 69 | + if self.use_start_end: |
| 70 | + self.add(self.start_token) |
| 71 | + self.add(self.end_token) |
| 72 | + |
| 73 | + def iterkeys(self): |
| 74 | + for k in self._mapping.keys(): |
| 75 | + if k == self.unk_token or k == self.mask_token: |
| 76 | + continue |
| 77 | + else: |
| 78 | + yield k |
| 79 | + |
| 80 | + def keys(self): |
| 81 | + return list(self.iterkeys()) |
| 82 | + |
| 83 | + def iteritems(self): |
| 84 | + for key, value in self._mapping.items(): |
| 85 | + if key == self.unk_token or key == self.mask_token: |
| 86 | + continue |
| 87 | + yield key, value |
| 88 | + |
| 89 | + def items(self): |
| 90 | + return list(self.iteritems()) |
| 91 | + |
| 92 | + def values(self): |
| 93 | + return [value for _, value in self.iteritems()] |
| 94 | + |
| 95 | + def __getitem__(self, k): |
| 96 | + if self._frozen: |
| 97 | + if k in self._mapping: |
| 98 | + out_index = self._mapping[k] |
| 99 | + elif self.use_unks: |
| 100 | + out_index = self.unk_index |
| 101 | + else: # case: frozen, don't want unks, raise exception |
| 102 | + raise VocabularyException("Vocabulary is frozen. " + |
| 103 | + "Key '{}' not found.".format(k)) |
| 104 | + if out_index in self._forced_unks: |
| 105 | + out_index = self.unk_index |
| 106 | + elif k in self._mapping: # case: normal |
| 107 | + out_index = self._mapping[k] |
| 108 | + self._counts[out_index] += 1 |
| 109 | + else: |
| 110 | + out_index = self._mapping[k] = self._i |
| 111 | + self._i += 1 |
| 112 | + self._flip[out_index] = k |
| 113 | + self._counts[out_index] = 1 |
| 114 | + |
| 115 | + return out_index |
| 116 | + |
| 117 | + def add(self, k): |
| 118 | + return self.__getitem__(k) |
| 119 | + |
| 120 | + def add_many(self, x): |
| 121 | + return [self.add(k) for k in x] |
| 122 | + |
| 123 | + def lookup(self, i): |
| 124 | + try: |
| 125 | + return self._flip[i] |
| 126 | + except KeyError: |
| 127 | + raise VocabularyException("Key {} not in Vocabulary".format(i)) |
| 128 | + |
| 129 | + def lookup_many(self, x): |
| 130 | + for k in x: |
| 131 | + yield self.lookup(k) |
| 132 | + |
| 133 | + def map(self, sequence, include_start_end=False): |
| 134 | + if include_start_end: |
| 135 | + yield self.start_index |
| 136 | + |
| 137 | + for item in sequence: |
| 138 | + yield self[item] |
| 139 | + |
| 140 | + if include_start_end: |
| 141 | + yield self.end_index |
| 142 | + |
| 143 | + def freeze(self, use_unks=False, frequency_cutoff=-1): |
| 144 | + self.use_unks = use_unks |
| 145 | + self._frequency_cutoff = frequency_cutoff |
| 146 | + |
| 147 | + if use_unks and self.unk_token not in self: |
| 148 | + self.add(self.unk_token) |
| 149 | + |
| 150 | + if self._frequency_cutoff > 0: |
| 151 | + for token, count in self._counts.items(): |
| 152 | + if count < self._frequency_cutoff: |
| 153 | + self._forced_unks.add(token) |
| 154 | + |
| 155 | + self._frozen = True |
| 156 | + |
| 157 | + def unfreeze(self): |
| 158 | + self._frozen = False |
| 159 | + |
| 160 | + def get_counts(self): |
| 161 | + return {self._flip[i]: count for i, count in self._counts.items()} |
| 162 | + |
| 163 | + def get_count(self, token=None, index=None): |
| 164 | + if token is None and index is None: |
| 165 | + return None |
| 166 | + elif token is not None and index is not None: |
| 167 | + print("Cannot do two things at once; choose one") |
| 168 | + elif token is not None: |
| 169 | + return self._counts[self[token]] |
| 170 | + elif index is not None: |
| 171 | + return self._counts[index] |
| 172 | + else: |
| 173 | + raise Exception("impossible condition") |
| 174 | + |
| 175 | + @property |
| 176 | + def unk_index(self): |
| 177 | + if self.unk_token not in self: |
| 178 | + return None |
| 179 | + return self._mapping[self.unk_token] |
| 180 | + |
| 181 | + @property |
| 182 | + def mask_index(self): |
| 183 | + if self.mask_token not in self: |
| 184 | + return None |
| 185 | + return self._mapping[self.mask_token] |
| 186 | + |
| 187 | + @property |
| 188 | + def start_index(self): |
| 189 | + if self.start_token not in self: |
| 190 | + return None |
| 191 | + return self._mapping[self.start_token] |
| 192 | + |
| 193 | + @property |
| 194 | + def end_index(self): |
| 195 | + if self.end_token not in self: |
| 196 | + return None |
| 197 | + return self._mapping[self.end_token] |
| 198 | + |
| 199 | + def __contains__(self, k): |
| 200 | + return k in self._mapping |
| 201 | + |
| 202 | + def __len__(self): |
| 203 | + return len(self._mapping) |
| 204 | + |
| 205 | + def __repr__(self): |
| 206 | + return "<Vocabulary(size={},frozen={})>".format(len(self), self._frozen) |
| 207 | + |
| 208 | + |
| 209 | + def get_serializable_contents(self): |
| 210 | + """ |
| 211 | + Creats a dict containing the necessary information to recreate this instance |
| 212 | + """ |
| 213 | + config = {"_mapping": self._mapping, |
| 214 | + "_flip": self._flip, |
| 215 | + "_frozen": self._frozen, |
| 216 | + "_i": self._i, |
| 217 | + "_counts": list(self._counts.items()), |
| 218 | + "_frequency_threshold": self._frequency_threshold, |
| 219 | + "use_unks": self.use_unks, |
| 220 | + "unk_token": self.unk_token, |
| 221 | + "use_mask": self.use_mask, |
| 222 | + "mask_token": self.mask_token, |
| 223 | + "use_start_end": self.use_start_end, |
| 224 | + "start_token": self.start_token, |
| 225 | + "end_token": self.end_token} |
| 226 | + return config |
| 227 | + |
| 228 | + @classmethod |
| 229 | + def deserialize_from_contents(cls, content): |
| 230 | + """ |
| 231 | + Recreate a Vocabulary instance; expect same dict as output in `serialize` |
| 232 | + """ |
| 233 | + try: |
| 234 | + _mapping = content.pop("_mapping") |
| 235 | + _flip = content.pop("_flip") |
| 236 | + _i = content.pop("_i") |
| 237 | + _frozen = content.pop("_frozen") |
| 238 | + _counts = content.pop("_counts") |
| 239 | + _frequency_threshold = content.pop("_frequency_threshold") |
| 240 | + except KeyError: |
| 241 | + raise Exception("unable to deserialize vocabulary") |
| 242 | + if isinstance(list(_flip.keys())[0], six.string_types): |
| 243 | + _flip = {int(k): v for k, v in _flip.items()} |
| 244 | + out = cls(**content) |
| 245 | + out._mapping = _mapping |
| 246 | + out._flip = _flip |
| 247 | + out._i = _i |
| 248 | + out._counts = Counter(dict(_counts)) |
| 249 | + out._frequency_threshold = _frequency_threshold |
| 250 | + |
| 251 | + if _frozen: |
| 252 | + out.freeze(out.use_unks) |
| 253 | + |
| 254 | + return out |
| 255 | + |
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