CODEWITHSUNDEEP
pythonregexregex-negationregex-lookarounds
Jonas Byström
Jonas Byström

Reputation: 26179

Three-in-one-regex

I have a very specific regex request. I need to match strings

When only using the first and last criteria this regex seems to work fine:

^.*m_.*(?<!Shape)$

But when I added the middle criteria I was lost.

Upvotes: 0

Views: 100

Answers (3)

nhahtdh
nhahtdh

Reputation: 56829

This can be achieved with normal string methods in Python (I add brackets for clarity):

("m_" in input) and ("phys_" not in input) and (not input.endswith("Shape"))

I interpret (always some characters after "m_") as a hint that "phys_" never appears in front of "m_", rather than allowing the case where "phys_" comes in front of "m_" to pass.

Upvotes: 0

Sergiu Toarca
Sergiu Toarca

Reputation: 2759

The regex you want is

^(?=.*m_)(?!.*phys_)(?!.*Shape$).*$

It will capture the entire string, and each condition is in it's own lookahead. You can test it and see a visualization of what's happening on www.debuggex.com.

Upvotes: 1

georg
georg

Reputation: 215029

import re

r = re.compile(r'^(?=.*m_)(?!.*m_.+phys_)(?!.+Shape$)')
print r.match("aaa")
print r.match("aaa m_ xx")
print r.match("aaa m_ xx Shape")
print r.match("aaa m_ xx phys_ foo")

Basically, the principle is:

  ^
  (?= .* should be there)
  (?! .* should not be there)

Upvotes: 2

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