tokenizer

Tokenization class for XLNet model.

class XLNetTokenizer(vocab_file, do_lower_case=False, remove_space=True, keep_accents=False, bos_token='<s>', eos_token='</s>', unk_token='<unk>', sep_token='<sep>', pad_token='<pad>', cls_token='<cls>', mask_token='<mask>', additional_special_tokens=['<eop>', '<eod>'], **kwargs)[source]

Bases: paddlenlp.transformers.tokenizer_utils.PretrainedTokenizer

Constructs an XLNet tokenizer based on SentencePiece.

This tokenizer inherits from PretrainedTokenizer which contains most of the main methods. For more information regarding those methods, please refer to this superclass.

Parameters
  • vocab_file (str) – The vocabulary file (ends with ‘.spm’) required to instantiate a SentencePiece tokenizer.

  • do_lower_case (bool, optional) – Whether or not to lowercase the input when tokenizing. Defaults to False and does not lowercase the input.

  • remove_space (bool, optional) – Whether or not to strip the text when tokenizing. Defaults to True and removes excess spaces before and after the string.

  • keep_accents (bool, optional) – Whether or not to keep accents when tokenizing. Defaults to False and does not keep accents.

  • bos_token (str, optional) – A special token representing the beginning of a sequence that was used during pretraining. Defaults to "<s>".

  • eos_token (str, optional) – A special token representing the end of a sequence that was used during pretraining. Defaults to "</s>".

  • unk_token (str, optional) – A special token representing the unknown (out-of-vocabulary) token. An unknown token is set to be unk_token inorder to be converted to an ID. Defaults to "<unk>".

  • sep_token (str, optional) – A special token separating two different sentences in the same input. Defaults to "<sep>".

  • pad_token (str, optional) – A special token used to make arrays of tokens the same size for batching purposes. Defaults to "<pad>".

  • cls_token (str, optional) – A special token used for sequence classification. It is the last token of the sequence when built with special tokens. Defaults to "<cls>".

  • mask_token (str, optional) – A special token representing a masked token. This is the token used in the masked language modeling task which the model tries to predict the original unmasked ones. Defaults to "<mask>".

  • additional_special_tokens (List[str], optional) – A list of additional special tokens to be used by the tokenizer. Defaults to ["<eop>", "<eod>"].

sp_model

The SentencePiece processor that is used for every conversion (string, tokens and IDs).

Type

SentencePieceProcessor

property vocab_size

Size of the base vocabulary (without the added tokens).

Type

int

get_vocab()[source]

Returns the vocabulary as a dictionary of token to index.

tokenizer.get_vocab()[token] is equivalent to tokenizer.convert_tokens_to_ids(token) when token is in the vocab.

Returns

The vocabulary.

Return type

Dict[str, int]

convert_tokens_to_string(tokens)[source]

Converts a sequence of tokens (list of string) to a single string by using ' '.join(tokens) .

Parameters

tokens (list[str]) – A sequence of tokens.

Returns

Converted string.

Return type

str

num_special_tokens_to_add(pair=False)[source]

Returns the number of added tokens when encoding a sequence with special tokens.

Parameters

pair (bool, optional) – Whether the input is a sequence pair or a single sequence. Defaults to False and the input is a single sequence.

Returns

Number of tokens added to sequences.

Return type

int

build_inputs_with_special_tokens(token_ids_0, token_ids_1=None)[source]

Builds model inputs from a sequence or a pair of sequence for sequence classification tasks by concatenating and adding special tokens. An XLNet sequence has the following format:

  • single sequence: X <sep> <cls>

  • pair of sequences: A <sep> B <sep> <cls>

Parameters
  • token_ids_0 (List[int]) – List of IDs for the first sequence.

  • token_ids_1 (List[int], optional) – Optional second list of IDs for the second sequenze. Defaults to None.

Returns

List of input IDs with the appropriate special tokens.

Return type

List[int]

build_offset_mapping_with_special_tokens(offset_mapping_0, offset_mapping_1=None)[source]

Builds offset map from a pair of offset map by concatenating and adding offsets of special tokens.

An XLNet offset_mapping has the following format:

  • single sequence: X (0,0) (0,0)

  • pair of sequences: A (0,0) B (0,0) (0,0)

Parameters
  • offset_mapping_0 (List[tuple]) – List of char offsets to which the special tokens will be added.

  • offset_mapping_1 (List[tuple], optional) – Optional second list of char offsets for offset mapping pairs. Defaults to None.

Returns

A list of char offsets with the appropriate offsets of special tokens.

Return type

List[tuple]

get_special_tokens_mask(token_ids_0, token_ids_1=None, already_has_special_tokens=False)[source]

Creates a special tokens mask from the input sequences. This method is called when adding special tokens using the tokenizer encode method.

Parameters
  • token_ids_0 (List[int]) – A list of inputs_ids for the first sequence.

  • token_ids_1 (List[int], optional) – Optional second list of inputs_ids for the second sequence. Defaults to None.

  • already_has_special_tokens (bool, optional) – Whether or not the token list already contains special tokens for the model. Defaults to False.

Returns

A list of integers which is either 0 or 1: 1 for a special token, 0 for a sequence token.

Return type

List[int]

create_token_type_ids_from_sequences(token_ids_0, token_ids_1=None)[source]

Creates a token_type mask from the input sequences. If token_ids_1 is not None, then a sequence pair token_type mask has the following format:

0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 2
| first sequence    | second sequence |

Else if token_ids_1 is None, then a single sequence token_type mask has the following format:

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2
|            first sequence           |
  • 0 stands for the segment id of first segment tokens,

  • 1 stands for the segment id of second segment tokens,

  • 2 stands for the segment id of cls_token.

Parameters
  • token_ids_0 (List[int]) – A list of inputs_ids for the first sequence.

  • token_ids_1 (List[int], optional) – Optional second list of inputs_ids for the second sequence. Defaults to None.

Returns

List of token type IDs according to the given sequence(s).

Return type

List[int]

save_resources(save_directory)[source]

Saves SentencePiece file (ends with ‘.spm’) under save_directory.

Parameters

save_directory (str) – Directory to save files into.