Using tokenizers from 🤗 Tokenizers ======================================================================================================================= The :class:`~transformers.PreTrainedTokenizerFast` depends on the `tokenizers `__ library. The tokenizers obtained from the 🤗 Tokenizers library can be loaded very simply into 🤗 Transformers. Before getting in the specifics, let's first start by creating a dummy tokenizer in a few lines: .. code-block:: >>> from tokenizers import Tokenizer >>> from tokenizers.models import BPE >>> from tokenizers.trainers import BpeTrainer >>> from tokenizers.pre_tokenizers import Whitespace >>> tokenizer = Tokenizer(BPE(unk_token="[UNK]")) >>> trainer = BpeTrainer(special_tokens=["[UNK]", "[CLS]", "[SEP]", "[PAD]", "[MASK]"]) >>> tokenizer.pre_tokenizer = Whitespace() >>> files = [...] >>> tokenizer.train(files, trainer) We now have a tokenizer trained on the files we defined. We can either continue using it in that runtime, or save it to a JSON file for future re-use. Loading directly from the tokenizer object ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Let's see how to leverage this tokenizer object in the 🤗 Transformers library. The :class:`~transformers.PreTrainedTokenizerFast` class allows for easy instantiation, by accepting the instantiated `tokenizer` object as an argument: .. code-block:: >>> from transformers import PreTrainedTokenizerFast >>> fast_tokenizer = PreTrainedTokenizerFast(tokenizer_object=tokenizer) This object can now be used with all the methods shared by the 🤗 Transformers tokenizers! Head to :doc:`the tokenizer page ` for more information. Loading from a JSON file ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In order to load a tokenizer from a JSON file, let's first start by saving our tokenizer: .. code-block:: >>> tokenizer.save("tokenizer.json") The path to which we saved this file can be passed to the :class:`~transformers.PreTrainedTokenizerFast` initialization method using the :obj:`tokenizer_file` parameter: .. code-block:: >>> from transformers import PreTrainedTokenizerFast >>> fast_tokenizer = PreTrainedTokenizerFast(tokenizer_file="tokenizer.json") This object can now be used with all the methods shared by the 🤗 Transformers tokenizers! Head to :doc:`the tokenizer page ` for more information.