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.
pattern in which case the latency would naturally accumulate.Ah, I've just seen the docs now "The compiled versions of the most recent patterns passed to re.compile() and the module-level matching functions are cached, so programs that use only a few regular expressions at a time needn’t worry about compiling regular expressions." so with this in mind, I can probably just remove the 'compile' step from all the scripts in this series. I haven't used it consistently to start with.
For those regexes only executed on a fraction of lines this is neligible, but it would be nice to keep them for those that run on every line. Jano
question 2) why do we need the '''.* and .*''' parts compared to the original perl regex? I'll go ahead and assume it's because re.match matches at the beginning of a string by default, in which case, shouldn't we use re.search which matches anywhere (that's what perl does by default) instead?Yeah, I didn't notice the 're.search' function existed & had the semantics closer to Perl. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
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