在单词边界匹配标点符号的正则表达式，包括下划线 [英] Regex that matches punctuation at the word boundary including underscore

问题描述

我正在为具有以下属性的变量短语寻找 Python 正则表达式:(为了举例，让我们假设这里的变量短语取值 and.但请注意，我需要以一种扮演 and 角色的方式来执行此操作code> 可以作为变量传入，我将其称为 phrase.)

I am looking for a Python regex for a variable phrase with the following properties: (For the sake of example, let's assume the variable phrase here is taking the value and. But note that I need to do this in a way that the thing playing the role of and can be passed in as a variable which I'll call phrase.)

应该匹配:this_and、this.and、(and)、[and]、and^、;And等

Should match: this_and, this.and, (and), [and], and^, ;And, etc.

不应该匹配:land, andy

这是我到目前为止所尝试的(其中 phrase 扮演 和 的角色):

This is what I tried so far (where phrase is playing the role of and):

pattern = r"\b  " + re.escape(phrase.lower()) + r"\b"            

这似乎适用于我的所有要求，只是它不匹配带有下划线的单词，例如\_hello、hello\_、hello_world.

This seems to work for all my requirements except that it does not match words with underscores e.g. \_hello, hello\_, hello_world.

理想情况下，我想使用标准库 re 模块而不是任何外部包.

Ideally I would like to use the standard library re module rather than any external packages.

推荐答案

您可以使用

r'(?<![^\W_])and(?![^\W_])'

查看正则表达式演示.使用 re.I 标志编译以启用不区分大小写的匹配.

See the regex demo. Compile with the re.I flag to enable case insensitive matching.

详情

• (?<![^\W_]) - 前面的字符不应是字母或数字字符
• and - 一些关键字
• (?![^\W_]) - 下一个字符不能是字母或数字

• (?<![^\W_]) - the preceding char should not be a letter or digit char
• and - some keyword
• (?![^\W_]) - the next char cannot be a letter or digit

Python 演示:

import re
strs = ['this_and', 'this.and', '(and)', '[and]', 'and^', ';And', 'land', 'andy']
phrase = "and"
rx = re.compile(r'(?<![^\W_]){}(?![^\W_])'.format(re.escape(phrase)), re.I)
for s in strs:
    print("{}: {}".format(s, bool(rx.search(s))))

输出:

this_and: True
this.and: True
(and): True
[and]: True
and^: True
;And: True
land: False
andy: False

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