> Now, re.findall() does cache the last 100 or so regexps, so it probably won't re-evaluate the regex each time. But really, pre-compute that regex with "_my_pattern = re.compile(regex) ... _my_pattern.findall()" and avoid even that cache lookup.

cpburns2009 says its 512 these days, which doesn't change the essence of my comment.

EDIT: The cache appears to be 512 on Python 3.6 so maybe precompiling isn't necessary unless you frequently use a large number of regular expressions.