用于行尾的 Python 正则表达式 [英] Python Regex for End of Line

问题描述

我正在尝试编写一个在点前后添加一个空格的正则表达式.但是，如果点后有空格或行尾，我只想要这个.

I am trying to write a regex which adds a space before and after a dot. However I only want this if there is a space or end of line after the dot.

但是，对于行尾情况，我无法这样做.

However I am unable to do so for end of line cases.

Eg.

I want a hotel. >> I want a hotel .
my email is [e-mail] >> my email is [e-mail]
I have to play. bye! >> I have to play . bye!

以下是我的代码:

# If "Dot and space" after word or number put space before and after
utterance = re.sub(r'(?<=[a-z0-9])[.][ $]',' . ',utterance)

如何更正我的正则表达式以确保上面的第一个示例也有效，我尝试将 $ 符号放在方括号中，但不起作用.

How do I correct my regex to make sure my 1st example above also works, I tried putting a $ sign in square bracket but that doesn't work.

推荐答案

主要问题是字符类中的 $ 表示文字 $ 符号，你只需要分组结构在这里.

The main issue is that $ inside a character class denotes a literal $ symbol, you just need a grouping construct here.

我建议使用以下代码:

import re
regex = r"([^\W_])\.(?:\s+|$)"
ss = ["I want a hotel.","my email is [e-mail]", "I have to play. bye!"]
for s in ss:
    result = re.sub(regex, r"\1 . ", s).rstrip()
    print(result)

查看 Python 演示

详情:

• ([^\W_]) - 第 1 组匹配任何字母或数字
• \. - 一个文字点
• (?:\s+|$) - 匹配 1+ 个空格或字符串结尾锚点的分组(这里，$ 匹配字符串结尾.)

• ([^\W_]) - Group 1 matching any letter or digit
• \. - a literal dot
• (?:\s+|$) - a grouping matching either 1+ whitespaces or end of string anchor (here, $ matches the end of string.)

rstrip 将删除替换时添加的尾随空格.

The rstrip will remove the trailing space added during replacement.

如果您使用的是 Python 3，默认情况下 [^\W_] 将匹配所有 Unicode 字母和数字.在 Python 2 中，re.U 标志将启用此行为.

If you are using Python 3, the [^\W_] will match all Unicode letters and digits by default. In Python 2, re.U flag will enable this behavior.

请注意，最后一个 (?:\s+|$) 中的 \s+ 会将多个空格缩小"为 1 个空格.

Note that \s+ in the last (?:\s+|$) will "shrink" multiple whitespaces into 1 space.

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