Question

This should be a pretty simple regex question but I couldn’t find any answers anywhere. How would one make a regex, which matches on either ONLY 2 characters, or at least 4 characters. Here is my current method of doing it (ignore the regex itself, that’s besides the point):

[A-Za-z0_9_]{2}|[A-Za-z0_9_]{4,}

However, this method takes twice the time (and is approximately 0.3s slower for me on a 400 line file), so I was wondering if there was a better way to do it?

Answer 1

Optimize the beginning, and anchor it.

^[A-Za-z0-9_]{2}(?:|[A-Za-z0-9_]{2,})$

(Also, you did say to ignore the regex itself, but I guessed you probably wanted 0-9, not 0_9)

EDIT Hm, I was sure I read that you want to match lines. Remove the anchors (^$) if you want to match inside the line as well. If you do match full lines only, anchors will speed you up (well, the front anchor ^ will, at least).