如何在python中使用带有可选字符的正则表达式? [英] How to use regex with optional characters in python?

问题描述

说我有一个字符串

"3434.35353"

和另一个字符串

"3593"

如果另一个失败，我如何制作一个能够匹配两者的单个正则表达式，而不必将模式设置为其他模式?我知道 \d+ 会匹配 3593，但它不会对 3434.35353 做任何事情，但是 (\d+\.\d+) 只会匹配带有小数的那个，并且不会返回 3593 的匹配项.

How do I make a single regular expression that is able to match both without me having to set the pattern to something else if the other fails? I know \d+ would match the 3593, but it would not do anything for the 3434.35353, but (\d+\.\d+) would only match the one with the decimal and return no matches found for the 3593.

我希望 m.group(1) 返回:

"3434.35353"

或

"3593"

推荐答案

您可以在一组字符后放置一个 ? 以使其可选.

You can put a ? after a group of characters to make it optional.

您想要一个点后跟任意数量的数字 \.\d+，组合在一起 (\.\d+)，可选 (\.\d+)?.坚持你的模式:

You want a dot followed by any number of digits \.\d+, grouped together (\.\d+), optionally (\.\d+)?. Stick that in your pattern:

import re
print re.match("(\d+(\.\d+)?)", "3434.35353").group(1)

3434.35353

print re.match("(\d+(\.\d+)?)", "3434").group(1)

3434

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