python – 使用NLTK自定义POS标记(错误)

我正在尝试将我自己的简单自定义标记器与nltk默认标记器结合使用,在本例中为perceptron标记器.

我的代码如下(基于this answer)：

import nltk.tag, nltk.data

default_tagger = nltk.data.load(nltk.tag._POS_TAGGER)
model = {'example_one': 'VB' 'example_two': 'NN'}
tagger = nltk.tag.UnigramTagger(model=model, backoff=default_tagger)

但是,这会产生以下错误：

  File "nltk_test.py", line 24, in <module>
    default_tagger = nltk.data.load(nltk.tag._POS_TAGGER)
  AttributeError: 'module' object has no attribute '_POS_TAGGER'

我试图通过将默认标记符更改为：

from nltk.tag.perceptron import PerceptronTagger
default_tagger = PerceptronTagger()

但后来我收到以下错误：

  File "nltk_test.py", line 26, in <module>
    tagger = nltk.tag.UnigramTagger(model=model, backoff=default_tagger)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/tag/sequential.py", line 340, in __init__
    backoff, cutoff, verbose)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/tag/sequential.py", line 284, in __init__
    ContextTagger.__init__(self, model, backoff)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/tag/sequential.py", line 125, in __init__
    SequentialBackoffTagger.__init__(self, backoff)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/nltk/tag/sequential.py", line 50, in __init__
    self._taggers = [self] + backoff._taggers
AttributeError: 'PerceptronTagger' object has no attribute '_taggers'

通过nltk.tag documentation查看似乎_POS_TAGGER不再存在.但是将其更改为_pos_tag或pos_tag也不起作用.

解决方法:

快速回答：现在使用nltk 3.0.1 pip install nltk == 3.0.1

更好的答案：他们去年9月更改了树库标记器并且还有很多其他后果(我们目前固定在3.0.1上,因为新的标记器至少对我们的需求更差).

这似乎工作,但我不确定代码是否正确：

class BackoffTagger:
    def __init__(self):
        self._taggers = [PerceptronTagger()]

model = {'example_one': 'VB', 'example_two': 'NN'}
tagger = nltk.tag.UnigramTagger(model=model, backoff=BackoffTagger())
tagger.tag(['example_one'])
>>> [('example_one', 'VB')]