Regex for existence of some words whose order doesn't matter

Tim picture Tim · Jul 9, 2014 · Viewed 11.7k times · Source

I would like to write a regex for searching for the existence of some words, but their order of appearance doesn't matter.

For example, search for "Tim" and "stupid". My regex is Tim.*stupid|stupid.*Tim. But is it possible to write a simpler regex (e.g. so that the two words appear just once in the regex itself)?

Answer

Unihedron picture Unihedron · Jul 9, 2014

See this regex:

/^(?=.*Tim)(?=.*stupid).+/

Regex explanation:

  • ^ Asserts position at start of string.
  • (?=.*Tim) Asserts that "Tim" is present in the string.
  • (?=.*stupid) Asserts that "stupid" is present in the string.
  • .+Now that our phrases are present, this string is valid. Go ahead and use .+ or - .++ to match the entire string.

To use lookaheads more exclusively, you can add another (?=.*<to_assert>) group. The entire regex can be simplified as /^(?=.*Tim).*stupid/.

See a regex demo!

>>> import re
>>> str ="""
... Tim is so stupid.
... stupid Tim!
... Tim foobar barfoo.
... Where is Tim?"""
>>> m = re.findall(r'^(?=.*Tim)(?=.*stupid).+$', str, re.MULTILINE)
>>> m
['Tim is so stupid.', 'stupid Tim!']
>>> m = re.findall(r'^(?=.*Tim).*stupid', str, re.MULTILINE)
>>> m
['Tim is so stupid.', 'stupid Tim!']

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