[makeworld]

That's because the Python regex module caches the regexes it compiles, so it only happens once. It's proper and good usage to specify the regex string inline, even in a hot path.

I'd only use a variable when I'm using the same regex multiple times in code, and even then I could still just have the variable be the string.

[masklinn]

> That's because the Python regex module caches the regexes it compiles, so it only happens once. It's proper and good usage to specify the regex string inline, even in a hot path.

Last time I had a look the regex cache was pretty small (few hundred entries) and gets completely cleared when full. Might have improved since, but historically it was very simplistic.

I disagree that it’s “proper and good usage” to specify regex inline. It’s fine for many usages but that’s as far as I’d go.

[makapuf]

Even then, hashing and lookup is completely unnecessary in a hot path. Having a variable with a compiled regex is not unpythonic AFAIK

[klyrs]

Yeah, it's been a while since I've benchmarked that, I'll try it out

[klyrs]

Gotta agree with the sibling comments here. The performance difference is definitely smaller than it used to be, but there's still good reasons to keep compiled regexes in a module scope.

Caveat: I write libraries, not "production" code; my requirements are significantly more strict. One thing I can't do is make assumptions about where my code will run. If you're using my library, and you compile a whole bunch of regexes, they'll evict my regexes from the cache. I don't want the performance of my library to suffer, so I'll keep them in the module scope.