Regex matching with multiple negative look behind conditions [duplicate]

Question

I would like to create a regex pattern that does not match multiple negative look behind patterns.

But if I try to compile a pattern like

import re
split_pattern = re.compile("(?<!AA|BAB|CAC|JHGS)[1-3]\s*(?=[A-Z])")

I get the error error: look-behind requires fixed-width pattern

Do you know a work-around this problem?

Kenzo Staelens · Accepted Answer · 2025-05-12 14:56:37Z

0

You should just be able to split up the negative lookbehind into multiple lookbehinds like so

(?<!AA)(?<!BAB)(?<!CAC)(?<!JHGS)[1-3]\s*(?=[A-Z])

Edit: As mentioned below in the comments, since BAB/CAC are the same size you could take those together

(?<!AA)(?<!BAB|CAC)(?<!JHGS)[1-3]\s*(?=[A-Z])

answered May 12 at 14:48

Kenzo Staelens

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1 Comment

Or (?<!AA)(?<!BAB|CAC)(?<!JHGS), because of same length.