python - 识别python中的动词时态

Question

如何使用Python + NLTK 来判断一个句子是否指代过去/现在/ future ？

我可以仅使用词性标记来做到这一点吗？这似乎有点不准确，在我看来我需要考虑句子上下文而不仅仅是单词。

对另一个可以做到这一点的图书馆有什么建议吗？

Answer 1

词性标记 - 它为您提供了让您查看动词时态的标记 - 已经考虑了句子上下文，因此它解决了您的问题。通过上下文的准确性。事实上，词性标注本身并不能很好地处理单词!从Ch. 5 of the NLTK book看这个例子给定句子中的上下文，让 NLTK 区分名词和动词给定的同音异义词(即给定像 permit 这样的词，它可以作为动词和名词具有不同的含义):

Let's look at another example, this time including some homonyms:

  >>> text = nltk.word_tokenize("They refuse to permit us to obtain the refuse permit")
  >>> nltk.pos_tag(text)
  [('They', 'PRP'), ('refuse', 'VBP'), ('to', 'TO'), ('permit', 'VB'), ('us', 'PRP'),
  ('to', 'TO'), ('obtain', 'VB'), ('the', 'DT'), ('refuse', 'NN'), ('permit', 'NN')]

Notice that refuse and permit both appear as a present tense verb(VBP) and a noun (NN). E.g. refUSE is a verb meaning "deny," whileREFuse is a noun meaning "trash" (i.e. they are not homophones). Thus,we need to know which word is being used in order to pronounce thetext correctly. (For this reason, text-to-speech systems usuallyperform POS-tagging.)