[Python-ideas] re.compile_lazy - on first use compiled regexes

Terry Reedy tjreedy at udel.edu
Thu Mar 28 00:06:36 CET 2013

On 3/24/2013 3:38 AM, Stefan Behnel wrote:
> Gregory P. Smith, 24.03.2013 00:48:
>> In the absense of profiling numbers showing otherwise, i'd rather see all
>> forms of manual caching like the conditional checks or a keep=True go away
>> as it's dirty and encourages premature "optimization".
> +1
> If I had been "more aware" of the re internal cache during the last years,
> I would have avoided at least a couple of re.compile() calls in my code, I
> guess.
> Maybe this is something that the documentation of re.compile() can help
> with, by telling people explicitly that this apparently cool feature of
> pre-compiling actually has a drawback in it (startup time + a bit of memory
> usage) and that they won't notice a runtime difference in most cases anyway.

With a decent re cache size, .compile seems more like an attractive 
nuisance that something useful.

Terry Jan Reedy

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