Tokenizer

Overview

Tokenization is a process of re-combining continuous character sequences into word sequences according to certain specifications. Reasonable tokenization is helpful for semantic comprehension.

MindSpore provides a tokenizer for multiple purposes to help you process text with high performance. You can build your own dictionaries, use appropriate tokenizers to split sentences into different tokens, and search for indexes of the tokens in the dictionaries.

MindSpore provides the following tokenizers. In addition, you can customize tokenizers as required.

Tokenizer	Description
BasicTokenizer	Performs tokenization on scalar text data based on specified rules.
BertTokenizer	Processes BERT text data.
JiebaTokenizer	Dictionary-based Chinese character string tokenizer.
RegexTokenizer	Performs tokenization on scalar text data based on a specified regular expression.
SentencePieceTokenizer	Performs tokenization based on the open-source tool package SentencePiece.
UnicodeCharTokenizer	Tokenizes scalar text data into Unicode characters.
UnicodeScriptTokenizer	Performs tokenization on scalar text data based on Unicode boundaries.
WhitespaceTokenizer	Performs tokenization on scalar text data based on spaces.
WordpieceTokenizer	Performs tokenization on scalar text data based on the word set.

For details about tokenizers, see MindSpore API.

MindSpore Tokenizers

The following describes how to use common tokenizers.

BertTokenizer

BertTokenizer performs tokenization by calling BasicTokenizer and WordpieceTokenizer.

The following example builds a text dataset and a character string list, uses BertTokenizer to perform tokenization on the dataset, and displays the text results before and after tokenization.

import mindspore.dataset as ds
import mindspore.dataset.text as text

input_list = ["床前明月光", "疑是地上霜", "举头望明月", "低头思故乡", "I am making small mistakes during working hours",
                "😀嘿嘿😃哈哈😄大笑😁嘻嘻", "繁體字"]
dataset = ds.NumpySlicesDataset(input_list, column_names=["text"], shuffle=False)

print("------------------------before tokenization----------------------------")

for data in dataset.create_dict_iterator(output_numpy=True):
    print(text.to_str(data['text']))

vocab_list = [
  "床", "前", "明", "月", "光", "疑", "是", "地", "上", "霜", "举", "头", "望", "低", "思", "故", "乡",
  "繁", "體", "字", "嘿", "哈", "大", "笑", "嘻", "i", "am", "mak", "make", "small", "mistake",
  "##s", "during", "work", "##ing", "hour", "😀", "😃", "😄", "😁", "+", "/", "-", "=", "12",
  "28", "40", "16", " ", "I", "[CLS]", "[SEP]", "[UNK]", "[PAD]", "[MASK]", "[unused1]", "[unused10]"]

vocab = text.Vocab.from_list(vocab_list)
tokenizer_op = text.BertTokenizer(vocab=vocab)
dataset = dataset.map(operations=tokenizer_op)

print("------------------------after tokenization-----------------------------")

for i in dataset.create_dict_iterator(num_epochs=1, output_numpy=True):
    print(text.to_str(i['text']))

The output is as follows:

------------------------before tokenization----------------------------
床前明月光
疑是地上霜
举头望明月
低头思故乡
I am making small mistakes during working hours
😀嘿嘿😃哈哈😄大笑😁嘻嘻
繁體字
------------------------after tokenization-----------------------------
['床' '前' '明' '月' '光']
['疑' '是' '地' '上' '霜']
['举' '头' '望' '明' '月']
['低' '头' '思' '故' '乡']
['I' 'am' 'mak' '##ing' 'small' 'mistake' '##s' 'during' 'work' '##ing'
 'hour' '##s']
['😀' '嘿' '嘿' '😃' '哈' '哈' '😄' '大' '笑' '😁' '嘻' '嘻']
['繁' '體' '字']

JiebaTokenizer

JiebaTokenizer performs Chinese tokenization based on Jieba.

The following example builds a text dataset, uses the HMM and MP dictionary files to create a JiebaTokenizer object, performs tokenization on the dataset, and displays the text results before and after tokenization.

import mindspore.dataset as ds
import mindspore.dataset.text as text

input_list = ["今天天气太好了我们一起去外面玩吧"]
dataset = ds.NumpySlicesDataset(input_list, column_names=["text"], shuffle=False)

print("------------------------before tokenization----------------------------")

for data in dataset.create_dict_iterator(output_numpy=True):
    print(text.to_str(data['text']))

# files from open source repository https://github.com/yanyiwu/cppjieba/tree/master/dict
HMM_FILE = "hmm_model.utf8"
MP_FILE = "jieba.dict.utf8"
jieba_op = text.JiebaTokenizer(HMM_FILE, MP_FILE)
dataset = dataset.map(operations=jieba_op, input_columns=["text"], num_parallel_workers=1)

print("------------------------after tokenization-----------------------------")

for i in dataset.create_dict_iterator(num_epochs=1, output_numpy=True):
    print(text.to_str(i['text']))

The output is as follows:

------------------------before tokenization----------------------------
今天天气太好了我们一起去外面玩吧
------------------------after tokenization-----------------------------
['今天天气' '太好了' '我们' '一起' '去' '外面' '玩吧']

SentencePieceTokenizer

SentencePieceTokenizer performs tokenization based on an open-source natural language processing tool package SentencePiece.

The following example builds a text dataset, creates a vocab object from the vocab_file file, uses SentencePieceTokenizer to perform tokenization on the dataset, and displays the text results before and after tokenization.

import mindspore.dataset as ds
import mindspore.dataset.text as text
from mindspore.dataset.text import SentencePieceModel, SPieceTokenizerOutType

input_list = ["I saw a girl with a telescope."]
dataset = ds.NumpySlicesDataset(input_list, column_names=["text"], shuffle=False)

print("------------------------before tokenization----------------------------")

for data in dataset.create_dict_iterator(output_numpy=True):
    print(text.to_str(data['text']))

# file from MindSpore repository https://gitee.com/mindspore/mindspore/blob/r1.1/tests/ut/data/dataset/test_sentencepiece/botchan.txt
vocab_file = "botchan.txt"
vocab = text.SentencePieceVocab.from_file([vocab_file], 5000, 0.9995, SentencePieceModel.UNIGRAM, {})
tokenizer_op = text.SentencePieceTokenizer(vocab, out_type=SPieceTokenizerOutType.STRING)
dataset = dataset.map(operations=tokenizer_op)

print("------------------------after tokenization-----------------------------")

for i in dataset.create_dict_iterator(num_epochs=1, output_numpy=True):
    print(text.to_str(i['text']))

The output is as follows:

------------------------before tokenization----------------------------
I saw a girl with a telescope.
------------------------after tokenization-----------------------------
['▁I' '▁sa' 'w' '▁a' '▁girl' '▁with' '▁a' '▁te' 'les' 'co' 'pe' '.']

UnicodeCharTokenizer

UnicodeCharTokenizer performs tokenization based on the Unicode character set.

The following example builds a text dataset, uses UnicodeCharTokenizer to perform tokenization on the dataset, and displays the text results before and after tokenization.

import mindspore.dataset as ds
import mindspore.dataset.text as text

input_list = ["Welcome to Beijing!", "北京欢迎您！ ", "我喜欢English!"]
dataset = ds.NumpySlicesDataset(input_list, column_names=["text"], shuffle=False)

print("------------------------before tokenization----------------------------")

for data in dataset.create_dict_iterator(output_numpy=True):
    print(text.to_str(data['text']))

tokenizer_op = text.UnicodeCharTokenizer()
dataset = dataset.map(operations=tokenizer_op)

print("------------------------after tokenization-----------------------------")

for i in dataset.create_dict_iterator(num_epochs=1, output_numpy=True):
    print(text.to_str(i['text']).tolist())

The output is as follows:

------------------------before tokenization----------------------------
Welcome to Beijing!
北京欢迎您！
我喜欢English!
------------------------after tokenization-----------------------------
['W', 'e', 'l', 'c', 'o', 'm', 'e', ' ', 't', 'o', ' ', 'B', 'e', 'i', 'j', 'i', 'n', 'g', '!']
['北', '京', '欢', '迎', '您', '！ ']
['我', '喜', '欢', 'E', 'n', 'g', 'l', 'i', 's', 'h', '!']

WhitespaceTokenizer

WhitespaceTokenizer performs tokenization based on spaces.

The following example builds a text dataset, uses WhitespaceTokenizer to perform tokenization on the dataset, and displays the text results before and after tokenization.

import mindspore.dataset as ds
import mindspore.dataset.text as text

input_list = ["Welcome to Beijing!", "北京欢迎您！ ", "我喜欢English!"]
dataset = ds.NumpySlicesDataset(input_list, column_names=["text"], shuffle=False)

print("------------------------before tokenization----------------------------")

for data in dataset.create_dict_iterator(output_numpy=True):
    print(text.to_str(data['text']))

tokenizer_op = text.WhitespaceTokenizer()
dataset = dataset.map(operations=tokenizer_op)

print("------------------------after tokenization-----------------------------")

for i in dataset.create_dict_iterator(num_epochs=1, output_numpy=True):
    print(text.to_str(i['text']).tolist())

The output is as follows:

------------------------before tokenization----------------------------
Welcome to Beijing!
北京欢迎您！
我喜欢English!
------------------------after tokenization-----------------------------
['Welcome', 'to', 'Beijing!']
['北京欢迎您！ ']
['我喜欢English!']

WordpieceTokenizer

WordpieceTokenizer performs tokenization based on the word set. A token can be a single word in the word set or a combination of words.

The following example builds a text dataset, creates a vocab object from the word list, uses WordpieceTokenizer to perform tokenization on the dataset, and displays the text results before and after tokenization.

import mindspore.dataset as ds
import mindspore.dataset.text as text

input_list = ["my", "favorite", "book", "is", "love", "during", "the", "cholera", "era", "what",
    "我", "最", "喜", "欢", "的", "书", "是", "霍", "乱", "时", "期", "的", "爱", "情", "您"]
vocab_english = ["book", "cholera", "era", "favor", "##ite", "my", "is", "love", "dur", "##ing", "the"]
vocab_chinese = ["我", '最', '喜', '欢', '的', '书', '是', '霍', '乱', '时', '期', '爱', '情']

dataset = ds.NumpySlicesDataset(input_list, column_names=["text"], shuffle=False)

print("------------------------before tokenization----------------------------")

for data in dataset.create_dict_iterator(output_numpy=True):
    print(text.to_str(data['text']))

vocab = text.Vocab.from_list(vocab_english+vocab_chinese)
tokenizer_op = text.WordpieceTokenizer(vocab=vocab)
dataset = dataset.map(operations=tokenizer_op)

print("------------------------after tokenization-----------------------------")

for i in dataset.create_dict_iterator(num_epochs=1, output_numpy=True):
    print(text.to_str(i['text']))

The output is as follows:

------------------------before tokenization----------------------------
my
favorite
book
is
love
during
the
cholera
era
what
我
最
喜
欢
的
书
是
霍
乱
时
期
的
爱
情
您
------------------------after tokenization-----------------------------
['my']
['favor' '##ite']
['book']
['is']
['love']
['dur' '##ing']
['the']
['cholera']
['era']
['[UNK]']
['我']
['最']
['喜']
['欢']
['的']
['书']
['是']
['霍']
['乱']
['时']
['期']
['的']
['爱']
['情']
['[UNK]']