如何使用 nltk 正则表达式模式提取特定的短语块?

问题描述

我编写了以下正则表达式来标记某些短语模式

pattern = """P2:{+?<JJ>* <NN>+ <VB>* <JJ>*}P1:{?<NN>+<CC>?<NN>* <VB>?<RB>* <JJ>+}P3:{}P4:{}"""

此模式将正确标记一个短语，例如:

a = '披萨很好，但意大利面很糟糕'

并用 2 个短语给出所需的输出:

1. 披萨很好吃
2. 意大利面很糟糕

但是，如果我的句子是这样的:

a = '披萨很棒而且很棒'

仅匹配短语:

'披萨棒极了'

而不是想要的:

'披萨很棒而且很棒'

如何在第二个示例中加入正则表达式模式?

解决方案

首先我们来看看NLTK给出的POS标签:

>>>从 nltk 导入 pos_tag>>>sent = '披萨棒极了'.split()>>>pos_tag(发送)[('The', 'DT'), ('pizza', 'NN'), ('was', 'VBD'), ('awesome', 'JJ'), ('and', 'CC'), ('辉煌', 'JJ')]>>>sent = '披萨很好，但意大利面很糟糕'.split()>>>pos_tag(发送)[('The', 'DT'), ('pizza', 'NN'), ('was', 'VBD'), ('good', 'JJ'), ('but', 'CC'), ('pasta', 'NN'), ('was', 'VBD'), ('bad', 'JJ')]

(注意:以上是 NLTK v3.1 pos_tag 的输出，旧版本可能有所不同)

你想要捕捉的本质是:

• NN VBD JJ CC JJ
• NN VBD JJ

所以让我们用这些模式来捕捉它们:

>>>从 nltk 导入 RegexpParser>>>sent1 = ['The', 'pizza', 'was', 'awesome', 'and', 'brilliant']>>>sent2 = ['The', 'pizza', 'was', 'good', 'but', 'pasta', 'was', 'bad']>>>模式 = """... P:{<NN><VBD><JJ><CC><JJ>}... {<NN><VBD><JJ>}……">>>PChunker = RegexpParser(模式)>>>PChunker.parse(pos_tag(sent1))Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('awesome', 'JJ'), ('and', 'CC'), ('brilliant', 'JJ')])])>>>PChunker.parse(pos_tag(sent2))Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('good', 'JJ')]), ('but', 'CC'), Tree('P', [('pasta', 'NN'), ('was', 'VBD'), ('bad', 'JJ')])])

这就是硬编码的欺骗"！！！

让我们回到 POS 模式:

• NN VBD JJ CC JJ
• NN VBD JJ

可以简化为:

• NN VBD JJ (CC JJ)

因此您可以在正则表达式中使用可选运算符，例如:

>>>模式 = """... P:{<NN><VBD><JJ>(<CC><JJ>)?}……">>>PChunker = RegexpParser(模式)>>>PChunker.parse(pos_tag(sent1))Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('awesome', 'JJ'), ('and', 'CC'), ('brilliant', 'JJ')])])>>>PChunker.parse(pos_tag(sent2))Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('good', 'JJ')]), ('but', 'CC'), Tree('P', [('pasta', 'NN'), ('was', 'VBD'), ('bad', 'JJ')])])

很可能您使用的是旧标记器，这就是您的模式不同的原因，但我想您已经了解如何使用上面的示例捕获所需的短语.

步骤是:

• 首先，使用pos_tag
检查POS模式是什么
• 然后概括模式并简化它们
• 然后将它们放入RegexpParser

I have written the following regex to tag certain phrases pattern

pattern = """
        P2: {<JJ>+ <RB>? <JJ>* <NN>+ <VB>* <JJ>*}
        P1: {<JJ>? <NN>+ <CC>? <NN>* <VB>? <RB>* <JJ>+}
        P3: {<NP1><IN><NP2>}
        P4: {<NP2><IN><NP1>}

    """

This pattern would correctly tag a phrase such as:

a = 'The pizza was good but pasta was bad'

and give the desired output with 2 phrases:

1. pizza was good
2. pasta was bad

However, if my sentence is something like:

a = 'The pizza was awesome and brilliant'

matches only the phrase:

'pizza was awesome'

instead of the desired:

'pizza was awesome and brilliant'

How do I incorporate the regex pattern for my second example as well?

解决方案

Firstly, let's take a look at the POS tags that NLTK gives:

>>> from nltk import pos_tag
>>> sent = 'The pizza was awesome and brilliant'.split()
>>> pos_tag(sent)
[('The', 'DT'), ('pizza', 'NN'), ('was', 'VBD'), ('awesome', 'JJ'), ('and', 'CC'), ('brilliant', 'JJ')]
>>> sent = 'The pizza was good but pasta was bad'.split()
>>> pos_tag(sent)
[('The', 'DT'), ('pizza', 'NN'), ('was', 'VBD'), ('good', 'JJ'), ('but', 'CC'), ('pasta', 'NN'), ('was', 'VBD'), ('bad', 'JJ')]

(Note: The above are the outputs from NLTK v3.1 pos_tag, older version might differ)

What you want to capture is essentially:

• NN VBD JJ CC JJ
• NN VBD JJ

So let's catch them with these patterns:

>>> from nltk import RegexpParser
>>> sent1 = ['The', 'pizza', 'was', 'awesome', 'and', 'brilliant']
>>> sent2 = ['The', 'pizza', 'was', 'good', 'but', 'pasta', 'was', 'bad']
>>> patterns = """
... P: {<NN><VBD><JJ><CC><JJ>}
... {<NN><VBD><JJ>}
... """
>>> PChunker = RegexpParser(patterns)
>>> PChunker.parse(pos_tag(sent1))
Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('awesome', 'JJ'), ('and', 'CC'), ('brilliant', 'JJ')])])
>>> PChunker.parse(pos_tag(sent2))
Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('good', 'JJ')]), ('but', 'CC'), Tree('P', [('pasta', 'NN'), ('was', 'VBD'), ('bad', 'JJ')])])

---

So that's "cheating" by hardcoding!!!

Let's go back to the POS patterns:

• NN VBD JJ CC JJ
• NN VBD JJ

Can be simplified to:

• NN VBD JJ (CC JJ)

So you can use the optional operators in the regex, e.g.:

>>> patterns = """
... P: {<NN><VBD><JJ>(<CC><JJ>)?}
... """
>>> PChunker = RegexpParser(patterns)
>>> PChunker.parse(pos_tag(sent1))
Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('awesome', 'JJ'), ('and', 'CC'), ('brilliant', 'JJ')])])
>>> PChunker.parse(pos_tag(sent2))
Tree('S', [('The', 'DT'), Tree('P', [('pizza', 'NN'), ('was', 'VBD'), ('good', 'JJ')]), ('but', 'CC'), Tree('P', [('pasta', 'NN'), ('was', 'VBD'), ('bad', 'JJ')])])

---

Most probably you're using the old tagger, that's why your patterns are different but I guess you see how you could capture the phrases you need using the example above.

The steps are:

• First, check what is the POS patterns using the pos_tag
• Then generalize patterns and simplify them
• Then put them into the RegexpParser

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