python正则表达式“\1" [英] python regular expression "\1"

问题描述

谁能告诉我以下 Python 正则表达式中的\1"是什么意思?

Can anyone tell me what does "\1" mean in the following regular expression in Python?

re.sub(r'(\b[a-z]+) \1', r'\1', 'cat in the the hat')

推荐答案

\1 等价于 re.search(...).group(1),正则表达式中第一个括号分隔的表达式.

\1 is equivalent to re.search(...).group(1), the first parentheses-delimited expression inside of the regex.

这也是一个有趣的事实，部分原因是正则表达式在 Python 和其他编程语言中比所需的要慢得多由 CS 理论.

It's also, fun fact, part of the reason that regular expressions are significantly slower in Python and other programming languages than required to be by CS theory.

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