tokenizer.py

import sentencepiece as spm

from pathlib import Path
from typing import Any, Dict, Iterable, List, NamedTuple, Set, Tuple, Union

import json
from abc import abstractmethod
from abc import ABC
import numpy as np


class BaseTokenizer(ABC):
    def __init__(
        self,
        token_list: Union[Path, str, Iterable[str]] = None,
        unk_symbol: str = "<unk>",
        **kwargs,
    ):

        if token_list is not None:
            if isinstance(token_list, (Path, str)) and token_list.endswith(".txt"):
                token_list = Path(token_list)
                self.token_list_repr = str(token_list)
                self.token_list: List[str] = []

                with token_list.open("r", encoding="utf-8") as f:
                    for idx, line in enumerate(f):
                        line = line.rstrip()
                        self.token_list.append(line)
            elif isinstance(token_list, (Path, str)) and token_list.endswith(".json"):
                token_list = Path(token_list)
                self.token_list_repr = str(token_list)
                self.token_list: List[str] = []

                with open(token_list, "r", encoding="utf-8") as f:
                    self.token_list = json.load(f)

            else:
                self.token_list: List[str] = list(token_list)
                self.token_list_repr = ""
                for i, t in enumerate(self.token_list):
                    if i == 3:
                        break
                    self.token_list_repr += f"{t}, "
                self.token_list_repr += f"... (NVocab={(len(self.token_list))})"

            self.token2id: Dict[str, int] = {}
            for i, t in enumerate(self.token_list):
                if t in self.token2id:
                    raise RuntimeError(f'Symbol "{t}" is duplicated')
                self.token2id[t] = i

            self.unk_symbol = unk_symbol
            if self.unk_symbol not in self.token2id:
                raise RuntimeError(f"Unknown symbol '{unk_symbol}' doesn't exist in the token_list")
            self.unk_id = self.token2id[self.unk_symbol]

    def encode(self, text, **kwargs):
        tokens = self.text2tokens(text)
        text_ints = self.tokens2ids(tokens)

        return text_ints

    def decode(self, text_ints):
        token = self.ids2tokens(text_ints)
        text = self.tokens2text(token)
        return text

    def get_num_vocabulary_size(self) -> int:
        return len(self.token_list)

    def ids2tokens(self, integers: Union[np.ndarray, Iterable[int]]) -> List[str]:
        if isinstance(integers, np.ndarray) and integers.ndim != 1:
            raise ValueError(f"Must be 1 dim ndarray, but got {integers.ndim}")
        return [self.token_list[i] for i in integers]

    def tokens2ids(self, tokens: Iterable[str]) -> List[int]:
        return [self.token2id.get(i, self.unk_id) for i in tokens]

    @abstractmethod
    def text2tokens(self, line: str) -> List[str]:
        raise NotImplementedError

    @abstractmethod
    def tokens2text(self, tokens: Iterable[str]) -> str:
        raise NotImplementedError
    

class SentencepiecesTokenizer(BaseTokenizer):
    def __init__(self, bpemodel: Union[Path, str], **kwargs):
        super().__init__(**kwargs)
        self.bpemodel = str(bpemodel)
        # NOTE(kamo):
        # Don't build SentencePieceProcessor in __init__()
        # because it's not picklable and it may cause following error,
        # "TypeError: can't pickle SwigPyObject objects",
        # when giving it as argument of "multiprocessing.Process()".
        self.sp = None
        self._build_sentence_piece_processor()

    def __repr__(self):
        return f'{self.__class__.__name__}(model="{self.bpemodel}")'

    def _build_sentence_piece_processor(self):
        # Build SentencePieceProcessor lazily.
        if self.sp is None:
            self.sp = spm.SentencePieceProcessor()
            self.sp.load(self.bpemodel)

    def text2tokens(self, line: str) -> List[str]:
        self._build_sentence_piece_processor()
        return self.sp.EncodeAsPieces(line)

    def tokens2text(self, tokens: Iterable[str]) -> str:
        self._build_sentence_piece_processor()
        return self.sp.DecodePieces(list(tokens))

    def encode(self, line: str, **kwargs) -> List[int]:
        self._build_sentence_piece_processor()
        return self.sp.EncodeAsIds(line)

    def decode(self, line: List[int], **kwargs):
        self._build_sentence_piece_processor()
        return self.sp.DecodeIds(line)

    def get_vocab_size(self):
        return self.sp.GetPieceSize()

    def ids2tokens(self, *args, **kwargs):
        return self.decode(*args, **kwargs)

    def tokens2ids(self, *args, **kwargs):
        return self.encode(*args, **kwargs)