使用正则表达式使用单词“but”来分块句子

Posted 2023-02-23

【中文标题】使用正则表达式使用单词“but”来分块句子

【英文标题】：Chunking sentences using the word 'but' with RegEx

【发布时间】：2019-01-31 12:37:46

【问题描述】：

我正在尝试在单词“but”（或任何其他并列连词）处使用 RegEx 对句子进行分块。它不工作......

sentence = nltk.pos_tag(word_tokenize("There are no large collections present but there is spinal canal stenosis."))
result = nltk.RegexpParser(grammar).parse(sentence)
DigDug = nltk.RegexpParser(r'CHUNK: .*<CC>.*')
for subtree in DigDug.parse(sentence).subtrees(): 
    if subtree.label() == 'CHUNK': print(subtree.node())

我需要将句子"There are no large collections present but there is spinal canal stenosis."分成两部分：

1. "There are no large collections present"
2. "there is spinal canal stenosis."

我还希望使用相同的代码在“and”和其他并列连词 (CC) 词处拆分句子。但是我的代码不起作用。请帮忙。

【参考方案1】：

我认为你可以简单地做

import re
result = re.split(r"\s+(?:but|and)\s+", sentence)

在哪里

`\s`        Match a single character that is a "whitespace character" (spaces, tabs, line breaks, etc.)
`+`         Between one and unlimited times, as many times as possible, giving back as needed (greedy)
`(?:`       Match the regular expression below, do not capture
            Match either the regular expression below (attempting the next alternative only if this one fails)
  `but`     Match the characters "but" literally
  `|`       Or match regular expression number 2 below (the entire group fails if this one fails to match)
  `and`     Match the characters "and" literally
)
`\s`        Match a single character that is a "whitespace character" (spaces, tabs, line breaks, etc.)
`+`         Between one and unlimited times, as many times as possible, giving back as needed (greedy)

您可以在其中添加更多连词，以竖线字符| 分隔。 请注意，这些单词不包含在正则表达式中具有特殊含义的字符。如果有疑问，请先使用re.escape(word) 避开​​它们

【参考方案2】：

如果您想避免硬编码“but”和“and”等连词，请尝试将 chinking 与 chunking 一起使用：

---

import nltk
Digdug = nltk.RegexpParser(r""" 
CHUNK_AND_CHINK:
<.*>+          # Chunk everything
<CC>+      # Chink sequences of CC
""")
sentence = nltk.pos_tag(nltk.word_tokenize("There are no large collections present but there is spinal canal stenosis."))

result = Digdug.parse(sentence)

for subtree in result.subtrees(filter=lambda t: t.label() == 
'CHUNK_AND_CHINK'):
            print (subtree)

Chinking 基本上排除了我们不需要的词组短语——在这种情况下是“但是”。 更多详情请见：http://www.nltk.org/book/ch07.html