How can I make regex not accept some values?

Question

I want my regex to match some values, but not accept others. The base regex is ^/.+/.+$

I want to not accept questions mark in the last / part, and not accept people or dungen as the first / part.

MATCH: /a/b/c/d
MATCH: /a/b
NO MATCH: /people/b/c/d
MATCH: /peoples/b/c/d
NO MATCH: /a/b/c?x=y

I know you can use [^ABCD] in order to NOT match characters, but it won't work with whole strings.

Any help?

Matt Ball · Accepted Answer · 2013-02-08 18:48:46Z

4

Rejecting question marks after the last / is easy - use a character class [^?] instead of .:

^/.+/[^?]+$

To reject people or dungen in between the two /s, you can use negative lookahead. Since you want to reject /people/ but accept /peoples/ the lookahead looks all the way to the end of the string.

^/(?!(?:people|dungen)/.+$).+/.+$

So combining the two:

^/(?!(?:people|dungen)/[^?]+$).+/[^?]+$

Let's test.

>>> import re
>>> r = re.compile(r'^/(?!(?:people|dungen)/[^?]+$).+/[^?]+$')
>>> for s in ['/a/b/c/d', '/a/b', '/people/b/c/d', '/peoples/b/c/d', '/a/b/c?x=y']:
...     print not not r.search(s)
...
True
True
False
True
False

edited Feb 8, 2013 at 18:48

answered Feb 8, 2013 at 18:33

Matt Ball

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Comments

MikeM · Accepted Answer · 2013-02-08 18:49:57Z

1

You could use

^/(?!(people|dungen)/).+/[^?]+$

answered Feb 8, 2013 at 18:49

MikeM

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