39 lines
1.5 KiB
Python
39 lines
1.5 KiB
Python
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from math import inf
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from typing import List, Tuple
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class TextTokenizer:
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def __init__(self, vocab: dict, merges: List[str]):
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self.token_from_subword = vocab
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pairs = [tuple(pair.split()) for pair in merges]
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self.rank_from_pair = dict(zip(pairs, range(len(pairs))))
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def __call__(self, text: str) -> List[int]:
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sep_token = self.token_from_subword['</s>']
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cls_token = self.token_from_subword['<s>']
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unk_token = self.token_from_subword['<unk>']
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text = text.lower().encode("ascii", errors="ignore").decode()
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tokens = [
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self.token_from_subword.get(subword, unk_token)
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for word in text.split(" ") if len(word) > 0
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for subword in self.get_byte_pair_encoding(word)
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]
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return [cls_token] + tokens + [sep_token]
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def get_byte_pair_encoding(self, word: str) -> List[str]:
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def get_pair_rank(pair: Tuple[str, str]) -> int:
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return self.rank_from_pair.get(pair, inf)
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subwords = [chr(ord(" ") + 256)] + list(word)
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while len(subwords) > 1:
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pairs = list(zip(subwords[:-1], subwords[1:]))
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pair_to_merge = min(pairs, key=get_pair_rank)
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if pair_to_merge not in self.rank_from_pair: break
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i = pairs.index(pair_to_merge)
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subwords = (
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(subwords[:i] if i > 0 else []) +
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[subwords[i] + subwords[i + 1]] +
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(subwords[i + 2:] if i + 2 < len(subwords) else [])
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)
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print(subwords)
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return subwords
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