python regular expression repeating pattern match

Question

I would like some thoughts on how to write a regular expression which validates a pattern

ex. .??2

one of more characters followed by two question marks followed by one or more numbers and if only if there is another repeating pattern then the seperator will be a semi colon.

more examples

--??9;.??50;,??3 - in this example I have the pattern repeating and that is why the semi colon

or

*??5 - a * followed by two qnestions marks followed by a number and no semi colon as there are no repeating groups

This is what i currently have

.+\?\?\d+(;|)+

nneonneo · Accepted Answer · 2012-09-19 01:56:34Z

1

The basic pattern is .+?\?\?\d+. We have made the first .+ non-greedy so it won't try to match the whole string right away. Use a repeated group to capture the subsequent patterns: r'(.+?\?\?\d+)(;.+?\?\?\d+)*'

edited Sep 19, 2012 at 1:56

answered Sep 19, 2012 at 1:36

nneonneo

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4 Comments

wadapav Over a year ago

import re num = ".??1000;" if re.search(r'(.+?\?\?\d+)(;.+?\?\?\d+)+',num): print "pass" else: print "fail" prints fail- but it should pass

nneonneo Over a year ago

Ha, good point. Fixed regex to use * instead of + on the repeated subsequence.

wadapav Over a year ago

so you say this is correct r'(.+?\?\?\d+)(;.+?\?\?\d+)*' then num = ".??1000;." prints pass when it should fail

nneonneo Over a year ago

But that does pass...you're using re.search which doesn't try to match the whole string, so it matches just the first 7 characters. If you want to anchor at both ends, put ^ at the start and $ at the end.

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