CODEWITHSUNDEEP
pythonregex
BnMcG
BnMcG

Reputation: 688

Regex: Don't match string which is already part of a word

This sounds like it shuold be something simple, so I think I might be missing something.

Say I want to use a regular expression to match the string "cat", I can do this fine, however, I don't want to match "concatenate" for example, or any other word that contains "cat", I just want "cat" on its own.

How would I achieve this? I considered something like the following:

(CAT|Cat|cat|)( )*

But this doesn't seem to work correctly. I can't add a space on either side in case "Cat" is the first word in the sentence/line.

Is there a way to exclude characters using regular expressions? Something like "Not A-z or 0-9 either side of "cat" "?

Upvotes: 1

Views: 704

Answers (2)

anubhava
anubhava

Reputation: 785008

You can just use word boundary:

\bcat\b

If you want to disallow certain characters only then use lookarounds:

(?<![a-zA-Z0-9])cat(?![a-zA-Z0-9])

Upvotes: 2

Sam
Sam

Reputation: 20486

Try word boundaries:

/\bcat\b/gi

Demo

A word boundary, \b, is a zero-length assertion that essentially looks for a word character followed by a non-word character or visa versa (\w\W|\W\w|^\w|\w$).

Upvotes: 3

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