python - NLP:根据给定语法验证句子

Question

我有一个英语句子语料库

sentences = [
    "Mary had a little lamb.",
    "John has a cute black pup.",
    "I ate five apples."
]

和语法(为了简单起见)

grammar = ('''
    NP: {<NNP><VBZ|VBD><DT><JJ>*<NN><.>} # NP
    ''')

我想过滤掉不符合语法的句子。是否有内置的 NLTK 函数可以实现这一点？在上面的示例中，前两个句子遵循我的语法模式，但不是最后一个。

Answer 1

长话短说

编写一个语法，检查它是否解析，遍历子树并寻找你正在寻找的非终端，例如NP

参见:

• Python (NLTK) - more efficient way to extract noun phrases?
• How to Traverse an NLTK Tree object?

代码:

import nltk

grammar = ('''
    NP: {<NNP><VBZ|VBD><DT><JJ>*<NN><.>} # NP
    ''')

sentences = [
    "Mary had a little lamb.",
    "John has a cute black pup.",
    "I ate five apples."
]

def has_noun_phrase(sentence):
    parsed = chunkParser.parse(pos_tag(word_tokenize(sentence)))
    for subtree in parsed:
        if type(subtree) == nltk.Tree and subtree.label() == 'NP':
            return True
    return False

chunkParser = nltk.RegexpParser(grammar)
for sentence in sentences:
    print(has_noun_phrase(sentence))