297 lines
10 KiB
Python
297 lines
10 KiB
Python
# -*- coding: utf-8 -*-
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# Natural Language Toolkit: Tokenizer Utilities
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#
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# Copyright (C) 2001-2019 NLTK Project
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# Author: Steven Bird <stevenbird1@gmail.com>
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# URL: <http://nltk.sourceforge.net>
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# For license information, see LICENSE.TXT
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from re import finditer
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from xml.sax.saxutils import escape, unescape
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def string_span_tokenize(s, sep):
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r"""
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Return the offsets of the tokens in *s*, as a sequence of ``(start, end)``
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tuples, by splitting the string at each occurrence of *sep*.
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>>> from nltk.tokenize.util import string_span_tokenize
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>>> s = '''Good muffins cost $3.88\nin New York. Please buy me
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... two of them.\n\nThanks.'''
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>>> list(string_span_tokenize(s, " "))
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[(0, 4), (5, 12), (13, 17), (18, 26), (27, 30), (31, 36), (37, 37),
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(38, 44), (45, 48), (49, 55), (56, 58), (59, 73)]
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:param s: the string to be tokenized
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:type s: str
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:param sep: the token separator
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:type sep: str
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:rtype: iter(tuple(int, int))
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"""
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if len(sep) == 0:
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raise ValueError("Token delimiter must not be empty")
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left = 0
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while True:
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try:
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right = s.index(sep, left)
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if right != 0:
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yield left, right
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except ValueError:
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if left != len(s):
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yield left, len(s)
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break
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left = right + len(sep)
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def regexp_span_tokenize(s, regexp):
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r"""
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Return the offsets of the tokens in *s*, as a sequence of ``(start, end)``
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tuples, by splitting the string at each successive match of *regexp*.
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>>> from nltk.tokenize.util import regexp_span_tokenize
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>>> s = '''Good muffins cost $3.88\nin New York. Please buy me
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... two of them.\n\nThanks.'''
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>>> list(regexp_span_tokenize(s, r'\s'))
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[(0, 4), (5, 12), (13, 17), (18, 23), (24, 26), (27, 30), (31, 36),
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(38, 44), (45, 48), (49, 51), (52, 55), (56, 58), (59, 64), (66, 73)]
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:param s: the string to be tokenized
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:type s: str
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:param regexp: regular expression that matches token separators (must not be empty)
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:type regexp: str
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:rtype: iter(tuple(int, int))
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"""
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left = 0
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for m in finditer(regexp, s):
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right, next = m.span()
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if right != left:
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yield left, right
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left = next
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yield left, len(s)
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def spans_to_relative(spans):
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r"""
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Return a sequence of relative spans, given a sequence of spans.
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>>> from nltk.tokenize import WhitespaceTokenizer
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>>> from nltk.tokenize.util import spans_to_relative
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>>> s = '''Good muffins cost $3.88\nin New York. Please buy me
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... two of them.\n\nThanks.'''
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>>> list(spans_to_relative(WhitespaceTokenizer().span_tokenize(s)))
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[(0, 4), (1, 7), (1, 4), (1, 5), (1, 2), (1, 3), (1, 5), (2, 6),
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(1, 3), (1, 2), (1, 3), (1, 2), (1, 5), (2, 7)]
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:param spans: a sequence of (start, end) offsets of the tokens
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:type spans: iter(tuple(int, int))
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:rtype: iter(tuple(int, int))
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"""
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prev = 0
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for left, right in spans:
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yield left - prev, right - left
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prev = right
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class CJKChars(object):
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"""
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An object that enumerates the code points of the CJK characters as listed on
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http://en.wikipedia.org/wiki/Basic_Multilingual_Plane#Basic_Multilingual_Plane
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This is a Python port of the CJK code point enumerations of Moses tokenizer:
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https://github.com/moses-smt/mosesdecoder/blob/master/scripts/tokenizer/detokenizer.perl#L309
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"""
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# Hangul Jamo (1100–11FF)
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Hangul_Jamo = (4352, 4607) # (ord(u"\u1100"), ord(u"\u11ff"))
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# CJK Radicals Supplement (2E80–2EFF)
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# Kangxi Radicals (2F00–2FDF)
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# Ideographic Description Characters (2FF0–2FFF)
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# CJK Symbols and Punctuation (3000–303F)
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# Hiragana (3040–309F)
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# Katakana (30A0–30FF)
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# Bopomofo (3100–312F)
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# Hangul Compatibility Jamo (3130–318F)
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# Kanbun (3190–319F)
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# Bopomofo Extended (31A0–31BF)
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# CJK Strokes (31C0–31EF)
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# Katakana Phonetic Extensions (31F0–31FF)
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# Enclosed CJK Letters and Months (3200–32FF)
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# CJK Compatibility (3300–33FF)
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# CJK Unified Ideographs Extension A (3400–4DBF)
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# Yijing Hexagram Symbols (4DC0–4DFF)
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# CJK Unified Ideographs (4E00–9FFF)
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# Yi Syllables (A000–A48F)
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# Yi Radicals (A490–A4CF)
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CJK_Radicals = (11904, 42191) # (ord(u"\u2e80"), ord(u"\ua4cf"))
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# Phags-pa (A840–A87F)
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Phags_Pa = (43072, 43135) # (ord(u"\ua840"), ord(u"\ua87f"))
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# Hangul Syllables (AC00–D7AF)
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Hangul_Syllables = (44032, 55215) # (ord(u"\uAC00"), ord(u"\uD7AF"))
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# CJK Compatibility Ideographs (F900–FAFF)
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CJK_Compatibility_Ideographs = (63744, 64255) # (ord(u"\uF900"), ord(u"\uFAFF"))
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# CJK Compatibility Forms (FE30–FE4F)
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CJK_Compatibility_Forms = (65072, 65103) # (ord(u"\uFE30"), ord(u"\uFE4F"))
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# Range U+FF65–FFDC encodes halfwidth forms, of Katakana and Hangul characters
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Katakana_Hangul_Halfwidth = (65381, 65500) # (ord(u"\uFF65"), ord(u"\uFFDC"))
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# Supplementary Ideographic Plane 20000–2FFFF
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Supplementary_Ideographic_Plane = (
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131072,
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196607,
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) # (ord(u"\U00020000"), ord(u"\U0002FFFF"))
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ranges = [
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Hangul_Jamo,
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CJK_Radicals,
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Phags_Pa,
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Hangul_Syllables,
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CJK_Compatibility_Ideographs,
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CJK_Compatibility_Forms,
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Katakana_Hangul_Halfwidth,
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Supplementary_Ideographic_Plane,
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]
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def is_cjk(character):
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"""
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Python port of Moses' code to check for CJK character.
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>>> CJKChars().ranges
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[(4352, 4607), (11904, 42191), (43072, 43135), (44032, 55215), (63744, 64255), (65072, 65103), (65381, 65500), (131072, 196607)]
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>>> is_cjk(u'\u33fe')
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True
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>>> is_cjk(u'\uFE5F')
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False
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:param character: The character that needs to be checked.
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:type character: char
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:return: bool
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"""
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return any(
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[
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start <= ord(character) <= end
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for start, end in [
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(4352, 4607),
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(11904, 42191),
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(43072, 43135),
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(44032, 55215),
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(63744, 64255),
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(65072, 65103),
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(65381, 65500),
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(131072, 196607),
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]
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]
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)
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def xml_escape(text):
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"""
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This function transforms the input text into an "escaped" version suitable
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for well-formed XML formatting.
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Note that the default xml.sax.saxutils.escape() function don't escape
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some characters that Moses does so we have to manually add them to the
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entities dictionary.
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>>> input_str = ''')| & < > ' " ] ['''
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>>> expected_output = ''')| & < > ' " ] ['''
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>>> escape(input_str) == expected_output
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True
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>>> xml_escape(input_str)
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')| & < > ' " ] ['
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:param text: The text that needs to be escaped.
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:type text: str
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:rtype: str
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"""
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return escape(
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text,
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entities={
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r"'": r"'",
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r'"': r""",
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r"|": r"|",
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r"[": r"[",
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r"]": r"]",
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},
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)
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def xml_unescape(text):
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"""
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This function transforms the "escaped" version suitable
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for well-formed XML formatting into humanly-readable string.
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Note that the default xml.sax.saxutils.unescape() function don't unescape
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some characters that Moses does so we have to manually add them to the
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entities dictionary.
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>>> from xml.sax.saxutils import unescape
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>>> s = ')| & < > ' " ] ['
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>>> expected = ''')| & < > \' " ] ['''
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>>> xml_unescape(s) == expected
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True
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:param text: The text that needs to be unescaped.
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:type text: str
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:rtype: str
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"""
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return unescape(
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text,
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entities={
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r"'": r"'",
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r""": r'"',
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r"|": r"|",
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r"[": r"[",
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r"]": r"]",
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},
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)
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def align_tokens(tokens, sentence):
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"""
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This module attempt to find the offsets of the tokens in *s*, as a sequence
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of ``(start, end)`` tuples, given the tokens and also the source string.
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>>> from nltk.tokenize import TreebankWordTokenizer
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>>> from nltk.tokenize.util import align_tokens
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>>> s = str("The plane, bound for St Petersburg, crashed in Egypt's "
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... "Sinai desert just 23 minutes after take-off from Sharm el-Sheikh "
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... "on Saturday.")
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>>> tokens = TreebankWordTokenizer().tokenize(s)
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>>> expected = [(0, 3), (4, 9), (9, 10), (11, 16), (17, 20), (21, 23),
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... (24, 34), (34, 35), (36, 43), (44, 46), (47, 52), (52, 54),
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... (55, 60), (61, 67), (68, 72), (73, 75), (76, 83), (84, 89),
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... (90, 98), (99, 103), (104, 109), (110, 119), (120, 122),
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... (123, 131), (131, 132)]
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>>> output = list(align_tokens(tokens, s))
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>>> len(tokens) == len(expected) == len(output) # Check that length of tokens and tuples are the same.
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True
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>>> expected == list(align_tokens(tokens, s)) # Check that the output is as expected.
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True
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>>> tokens == [s[start:end] for start, end in output] # Check that the slices of the string corresponds to the tokens.
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True
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:param tokens: The list of strings that are the result of tokenization
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:type tokens: list(str)
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:param sentence: The original string
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:type sentence: str
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:rtype: list(tuple(int,int))
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"""
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point = 0
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offsets = []
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for token in tokens:
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try:
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start = sentence.index(token, point)
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except ValueError:
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raise ValueError('substring "{}" not found in "{}"'.format(token, sentence))
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point = start + len(token)
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offsets.append((start, point))
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return offsets
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