Regular expression incorrect output by python

Question

import os,re
def test():
    list  = re.findall(r'(255\.){2}','255.255.252.255.255.12')
    print list
if __name__ == '__main__':
test()

the output ：“['255.', '255.']”

why not 【255.255，255.255】？

the mactch object should is "255.255"

How can i get the correct output result?

Blender · Accepted Answer · 2012-12-08 03:12:05Z

2

In your regex, you're only capturing the first 255.. You need to wrap everything you want to capture in a capturing group:

>>> re.findall(r'((?:255\.){2})','255.255.252.255.255.12')
['255.255.', '255.255.']

(?:...) is a non-capturing group. It basically lets you group things without having them show up as a captured group.

answered Dec 8, 2012 at 3:12

Blender

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Comments

Santiclause · Accepted Answer · 2012-12-08 03:14:55Z

1

Mm, not quite. First off, you'll want a non-capturing group - the capturing group you have there will only capture '255.', and use that as the output for re.findall.

Example:

re.findall(r'(?:255\.){2}', '255.255.252.255.255.12')

The (?:) construct is a non-capturing group - and without any capturing groups, re.findall returns the entire matching string.

Note that this won't actually return ['255.255', '255.255'] - it will actually return ['255.255.', '255.255.'].

answered Dec 8, 2012 at 3:14

Santiclause

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