Regex and the OR operator without grouping in Python?

Question

Here are the cases. I'm looking for the following pattern in a log file.

All strings are in the form of AB_N or CDE_N. AB and CDE are fixed letters, followed by an underscore. N can be either 2 or 3 numbers.

I tried (AB|CDE)_\d{2,3} but that returns a group. I can't do \w{2,3}\d{2,3} because it has to be either AB or CDE and not AC or FEG. Omitting the parentheses breaks too. I am sure the solution is simple but I'm new to python and regex and can't figure this out.

You can wrap the entire thing in a group: `((AB|CDE)_\d{2,3})`, and the first group is `AB_123` and the second is just `AB`. — Andy Lester, Dec 20 '12 at 04:07

mattmc3 · Accepted Answer · 2015-06-24T23:32:57.140

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A ?: inside a parenthesis in a regex makes it non-capturing. Like so: (?:AB|CDE)_\d{2,3}

See docs here: http://docs.python.org/3/library/re.html About a third of the way through it goes over the non-capturing syntax.

edited Jun 24 '15 at 23:32

answered Dec 20 '12 at 03:48

mattmc3

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BrenBarn · Answer 2 · 2012-12-20T03:54:42.893

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The non-capturing group syntax is (?:...). So do (?:AB|CDE)_\d{2,3}. This is documented along with everything else.

edited Dec 20 '12 at 03:54

answered Dec 20 '12 at 03:47

BrenBarn

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Oops, a typo. But it looks like you made one too, since it should be `(?:AB|CDE)`. – BrenBarn Dec 20 '12 at 03:55
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Can I do something like `(?:abc|def|ghi|xyz)`? – qed Jun 08 '14 at 16:08
@qed - Yes, you can do anything you would do in regular parens. The `?:` just tells the regex not to treat those parens as a capturing group. – mattmc3 Nov 27 '18 at 19:59

Regex and the OR operator without grouping in Python?

2 Answers2