On Thu, Sep 26, 2019 at 05:34:49PM +0200, Ján Tomko wrote:
> On Thu, Sep 26, 2019 at 02:16:04PM +0100, Daniel P. Berrangé wrote:
> > On Thu, Sep 26, 2019 at 12:39:39PM +0200, Erik Skultety wrote:
> > > On Tue, Sep 24, 2019 at 03:58:44PM +0100, Daniel P. Berrangé wrote:
> > > question 1) what's the benefit of compiling a regex and using it only once? Btw
> > > python does cache every pattern passed to re.match (and friends) so compilation
> > > IMO hardly ever makes sense unless you're doing 1000s of searches for the same
>
> Some of the scripts here are run on the whole libvirt codebase so that
> is the case here. For example just removing the pre-compilation of
> regexes for comments from the spacing check script bumped the execution
> time from 6.5s to 7.4s
>
> Sadly, the one script where pre-compilation matters the most is the one
> where separating them puts them far away from the usage to not fit on
> one screen.
I could do a little custom function that caches all regexes
recache = {}
def research(regex, line):
global recache
if regex not in recache:
recache[regex] = re.compile(regex)
return recache[regex].search(line)
then the loop we can do a normal
research(r'''some regex''', line)
so we can get readability and full caching together. Probably not worth
repeating this trick for every script, but certainly the whitespace
script and a few others probably benefit.
Regards,
Daniel
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