Source Code for Package nltk.tag

  1  # Natural Language Toolkit: Taggers 
  2  # 
  3  # Copyright (C) 2001-2008 NLTK Project 
  4  # Author: Edward Loper <[email protected]> 
  5  #         Steven Bird <[email protected]> (minor additions) 
  6  # URL: <http://nltk.org> 
  7  # For license information, see LICENSE.TXT 
  8   
  9  """ 
 10  Classes and interfaces for tagging each token of a sentence with 
 11  supplementary information, such as its part of speech.  This task, 
 12  which is known as X{tagging}, is defined by the L{TaggerI} interface. 
 13  """ 
 14   
 15  from api import * 
 16  from util import * 
 17  from simplify import * 
 18  from sequential import * 
 19  from brill import * 
 20   
 21  __all__ = [ 
 22      # Tagger interface 
 23      'TaggerI', 
 24       
 25      # Should these be included:? 
 26      #'SequentialBackoffTagger', 'ContextTagger', 
 27   
 28      # Sequential backoff taggers. 
 29      'DefaultTagger', 'UnigramTagger', 'BigramTagger', 'TrigramTagger', 
 30      'NgramTagger', 'AffixTagger', 'RegexpTagger', 
 31   
 32      # Brill tagger -- trainer names? 
 33      'BrillTagger', 'BrillTaggerTrainer', 'FastBrillTaggerTrainer', 
 34   
 35      # Utilities.  Note: conversion functions x2y are intentionally 
 36      # left out; they should be accessed as nltk.tag.x2y().  Similarly 
 37      # for nltk.tag.accuracy. 
 38      'untag',  
 39      ] 
 40   
 41  # Import hmm module if numpy is installed 
 42  try: 
 43      import numpy 
 44      from hmm import * 
 45      __all__ += ['HiddenMarkovModelTagger', 'HiddenMarkovModelTrainer',] 
 46      # [xx] deprecated HiddenMarkovModel etc objects? 
 47  except ImportError: 
 48      pass 
 49   
 50   
 51  ###################################################################### 
 52  #{ Deprecated 
 53  ###################################################################### 
 54  from nltk.internals import Deprecated 
 55 -class TagI(TaggerI, Deprecated): 
 56      """Use nltk.TaggerI instead.""" 
 57 -class SequentialBackoff(SequentialBackoffTagger, Deprecated): 
 58      """Use nltk.SequentialBackoffTagger instead.  Note: the methods 
 59      used to subclass SequentialBackoffTagger do not match those of 
 60      the old nltk.tag.SequentialBackoff; see the api docs for info.""" 
 61 -class Ngram(SequentialBackoffTagger, Deprecated): 
 62      """Use nltk.NgramTagger instead.  Note: NgramTagger.train() is now 
 63      a factory method.""" 
 64 -    def __init__(self, n, cutoff=1, backoff=None): 
 65          SequentialBackoffTagger.__init__(self, backoff) 
 66          self._cutoff = cutoff 
 67          self._n = n 
 68 -    def train(self, tagged_corpus, verbose=False): 
 69          self._tagger = NgramTagger.train( 
 70              tagged_corpus, self._n, self.backoff, self._cutoff, verbose) 
 71 -    def choose_tag(self, tokens, index, history): 
 72          return self._tagger.choose_tag(tokens, index, history) 
 73 -class Unigram(Ngram, Deprecated): 
 74      """Use nltk.UnigramTagger instead.""" 
 75 -    def __init__(self, cutoff=1, backoff=None): 
 76          Ngram.__init__(self, 1, cutoff, backoff) 
 77 -class Bigram(Ngram, Deprecated): 
 78      """Use nltk.BigramTagger instead.""" 
 79 -    def __init__(self, cutoff=1, backoff=None): 
 80          Ngram.__init__(self, 2, cutoff, backoff) 
 81 -class Trigram(Ngram, Deprecated): 
 82      """Use nltk.TrigramTagger instead.""" 
 83 -    def __init__(self, cutoff=1, backoff=None): 
 84          Ngram.__init__(self, 3, cutoff, backoff) 
 85 -class Affix(SequentialBackoffTagger, Deprecated): 
 86      """Use nltk.AffixTagger instead.""" 
 87 -    def __init__(self, length, minlength, backoff=None): 
 88          SequentialBackoffTagger.__init__(self, backoff) 
 89          self._len = length 
 90          self._minlen = minlength 
 91          self._cutoff = cutoff 
 92 -    def train(self, tagged_corpus): 
 93          self._tagger = AffixTagger.train( 
 94              tagged_corpus, self._minlen, self._len, self.backoff) 
 95 -    def choose_tag(self, tokens, index, history): 
 96          return self._tagger.choose_tag(tokens, index, history) 
 97 -class Lookup(UnigramTagger, Deprecated): 
 98      """Use UnigramTagger instead.""" 
 99 -class Regexp(RegexpTagger, Deprecated): 
100      """Use RegexpTagger instead.""" 
101