Source code for nltk.tokenize

# -*- coding: utf-8 -*-
# Natural Language Toolkit: Tokenizers
#
# Copyright (C) 2001-2017 NLTK Project
# Author: Edward Loper <edloper@gmail.com>
#         Steven Bird <stevenbird1@gmail.com> (minor additions)
# Contributors: matthewmc, clouds56
# URL: <http://nltk.org/>
# For license information, see LICENSE.TXT

r"""
NLTK Tokenizer Package

Tokenizers divide strings into lists of substrings.  For example,
tokenizers can be used to find the words and punctuation in a string:

    >>> from nltk.tokenize import word_tokenize
    >>> s = '''Good muffins cost $3.88\nin New York.  Please buy me
    ... two of them.\n\nThanks.'''
    >>> word_tokenize(s)
    ['Good', 'muffins', 'cost', '$', '3.88', 'in', 'New', 'York', '.',
    'Please', 'buy', 'me', 'two', 'of', 'them', '.', 'Thanks', '.']

This particular tokenizer requires the Punkt sentence tokenization
models to be installed. NLTK also provides a simpler,
regular-expression based tokenizer, which splits text on whitespace
and punctuation:

    >>> from nltk.tokenize import wordpunct_tokenize
    >>> wordpunct_tokenize(s)
    ['Good', 'muffins', 'cost', '$', '3', '.', '88', 'in', 'New', 'York', '.',
    'Please', 'buy', 'me', 'two', 'of', 'them', '.', 'Thanks', '.']

We can also operate at the level of sentences, using the sentence
tokenizer directly as follows:

    >>> from nltk.tokenize import sent_tokenize, word_tokenize
    >>> sent_tokenize(s)
    ['Good muffins cost $3.88\nin New York.', 'Please buy me\ntwo of them.', 'Thanks.']
    >>> [word_tokenize(t) for t in sent_tokenize(s)]
    [['Good', 'muffins', 'cost', '$', '3.88', 'in', 'New', 'York', '.'],
    ['Please', 'buy', 'me', 'two', 'of', 'them', '.'], ['Thanks', '.']]

Caution: when tokenizing a Unicode string, make sure you are not
using an encoded version of the string (it may be necessary to
decode it first, e.g. with ``s.decode("utf8")``.

NLTK tokenizers can produce token-spans, represented as tuples of integers
having the same semantics as string slices, to support efficient comparison
of tokenizers.  (These methods are implemented as generators.)

    >>> from nltk.tokenize import WhitespaceTokenizer
    >>> list(WhitespaceTokenizer().span_tokenize(s))
    [(0, 4), (5, 12), (13, 17), (18, 23), (24, 26), (27, 30), (31, 36), (38, 44),
    (45, 48), (49, 51), (52, 55), (56, 58), (59, 64), (66, 73)]

There are numerous ways to tokenize text.  If you need more control over
tokenization, see the other methods provided in this package.

For further information, please see Chapter 3 of the NLTK book.
"""

import re

from nltk.data              import load
from nltk.tokenize.casual   import (TweetTokenizer, casual_tokenize)
from nltk.tokenize.mwe      import MWETokenizer
from nltk.tokenize.punkt    import PunktSentenceTokenizer
from nltk.tokenize.regexp   import (RegexpTokenizer, WhitespaceTokenizer,
                                    BlanklineTokenizer, WordPunctTokenizer,
                                    wordpunct_tokenize, regexp_tokenize,
                                    blankline_tokenize)
from nltk.tokenize.repp     import ReppTokenizer
from nltk.tokenize.sexpr    import SExprTokenizer, sexpr_tokenize
from nltk.tokenize.simple   import (SpaceTokenizer, TabTokenizer, LineTokenizer,
                                    line_tokenize)
from nltk.tokenize.stanford import StanfordTokenizer
from nltk.tokenize.texttiling import TextTilingTokenizer
from nltk.tokenize.toktok   import ToktokTokenizer
from nltk.tokenize.treebank import TreebankWordTokenizer
from nltk.tokenize.util     import string_span_tokenize, regexp_span_tokenize
from nltk.tokenize.stanford_segmenter import StanfordSegmenter


# Standard sentence tokenizer.
[docs]def sent_tokenize(text, language='english'): """ Return a sentence-tokenized copy of *text*, using NLTK's recommended sentence tokenizer (currently :class:`.PunktSentenceTokenizer` for the specified language). :param text: text to split into sentences :param language: the model name in the Punkt corpus """ tokenizer = load('tokenizers/punkt/{0}.pickle'.format(language)) return tokenizer.tokenize(text)
# Standard word tokenizer. _treebank_word_tokenizer = TreebankWordTokenizer() # See discussion on https://github.com/nltk/nltk/pull/1437 # Adding to TreebankWordTokenizer, the splits on # - chervon quotes u'\xab' and u'\xbb' . # - unicode quotes u'\u2018', u'\u2019', u'\u201c' and u'\u201d' improved_open_quote_regex = re.compile(u'([«“‘])', re.U) improved_close_quote_regex = re.compile(u'([»”’])', re.U) improved_punct_regex = re.compile(r'([^\.])(\.)([\]\)}>"\'' u'»”’ ' r']*)\s*$', re.U) _treebank_word_tokenizer.STARTING_QUOTES.insert(0, (improved_open_quote_regex, r' \1 ')) _treebank_word_tokenizer.ENDING_QUOTES.insert(0, (improved_close_quote_regex, r' \1 ')) _treebank_word_tokenizer.PUNCTUATION.insert(0, (improved_punct_regex, r'\1 \2 \3 '))
[docs]def word_tokenize(text, language='english', preserve_line=False): """ Return a tokenized copy of *text*, using NLTK's recommended word tokenizer (currently an improved :class:`.TreebankWordTokenizer` along with :class:`.PunktSentenceTokenizer` for the specified language). :param text: text to split into words :param text: str :param language: the model name in the Punkt corpus :type language: str :param preserve_line: An option to keep the preserve the sentence and not sentence tokenize it. :type preserver_line: bool """ sentences = [text] if preserve_line else sent_tokenize(text, language) return [token for sent in sentences for token in _treebank_word_tokenizer.tokenize(sent)]