BertTokenizer
classkeras_nlp.tokenizers.BertTokenizer(vocabulary=None, lowercase=False, **kwargs)
A BERT tokenizer using WordPiece subword segmentation.
This tokenizer class will tokenize raw strings into integer sequences and
is based on keras_nlp.tokenizers.WordPieceTokenizer
. Unlike the
underlying tokenizer, it will check for all special tokens needed by BERT
models and provides a from_preset()
method to automatically download
a matching vocabulary for a BERT preset.
If input is a batch of strings (rank > 0), the layer will output a
tf.RaggedTensor
where the last dimension of the output is ragged.
If input is a scalar string (rank == 0), the layer will output a dense
tf.Tensor
with static shape [None]
.
Arguments
True
, the input text will be first lowered before
tokenization.Examples
# Unbatched input.
tokenizer = keras_nlp.models.BertTokenizer.from_preset(
"bert_base_en_uncased",
)
tokenizer("The quick brown fox jumped.")
# Batched input.
tokenizer(["The quick brown fox jumped.", "The fox slept."])
# Detokenization.
tokenizer.detokenize(tokenizer("The quick brown fox jumped."))
# Custom vocabulary.
vocab = ["[UNK]", "[CLS]", "[SEP]", "[PAD]", "[MASK]"]
vocab += ["The", "quick", "brown", "fox", "jumped", "."]
tokenizer = keras_nlp.models.BertTokenizer(vocabulary=vocab)
tokenizer("The quick brown fox jumped.")
from_preset
methodBertTokenizer.from_preset(preset, **kwargs)
Instantiate a keras_nlp.models.Tokenizer
from a model preset.
A preset is a directory of configs, weights and other file assets used
to save and load a pre-trained model. The preset
can be passed as
one of:
'bert_base_en'
'kaggle://user/bert/keras/bert_base_en'
'hf://user/bert_base_en'
'./bert_base_en'
For any Tokenizer
subclass, you can run cls.presets.keys()
to list
all built-in presets available on the class.
This constructor can be called in one of two ways. Either from the base
class like keras_nlp.models.Tokenizer.from_preset()
, or from
a model class like keras_nlp.models.GemmaTokenizer.from_preset()
.
If calling from the base class, the subclass of the returning object
will be inferred from the config in the preset directory.
Arguments
True
, the weights will be loaded into the
model architecture. If False
, the weights will be randomly
initialized.Examples
# Load a preset tokenizer.
tokenizer = keras_nlp.tokenizer.Tokenizer.from_preset("bert_base_en")
# Tokenize some input.
tokenizer("The quick brown fox tripped.")
# Detokenize some input.
tokenizer.detokenize([5, 6, 7, 8, 9])
Preset name | Parameters | Description |
---|---|---|
bert_tiny_en_uncased | 4.39M | 2-layer BERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus. |
bert_small_en_uncased | 28.76M | 4-layer BERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus. |
bert_medium_en_uncased | 41.37M | 8-layer BERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus. |
bert_base_en_uncased | 109.48M | 12-layer BERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus. |
bert_base_en | 108.31M | 12-layer BERT model where case is maintained. Trained on English Wikipedia + BooksCorpus. |
bert_base_zh | 102.27M | 12-layer BERT model. Trained on Chinese Wikipedia. |
bert_base_multi | 177.85M | 12-layer BERT model where case is maintained. Trained on trained on Wikipedias of 104 languages |
bert_large_en_uncased | 335.14M | 24-layer BERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus. |
bert_large_en | 333.58M | 24-layer BERT model where case is maintained. Trained on English Wikipedia + BooksCorpus. |
bert_tiny_en_uncased_sst2 | 4.39M | The bert_tiny_en_uncased backbone model fine-tuned on the SST-2 sentiment analysis dataset. |