[Python-Dev] Investigating time for `import requests`

[Barry Warsaw]

On Oct 1, 2017, at 22:34, Nathaniel Smith <njs at pobox.com> wrote:
> 
> In principle re.compile() itself could be made lazy -- return a
> regular exception object that just holds the string, and then compiles
> and caches it the first time it's used. Might be tricky to do in a
> backwards compatibility way if it moves detection of invalid regexes
> from compile time to use time, but it could be an opt-in flag.

I already tried that experiment.  1) there are tricky corner cases; 2) nobody liked the change in semantics when re.compile() was made lazy.

https://bugs.python.org/issue31580
https://github.com/python/cpython/pull/3755

I think there are opportunities for an explicit API for lazy compilation of regular expressions, but I’m skeptical of the adoption curve making it worthwhile.  But maybe I’m wrong!

-Barry

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