El lun, 17 ene 2022 a las 7:11, Steven D'Aprano (<st...@pearwood.info>)
escribió:
> On Mon, Jan 17, 2022 at 11:18:13PM +0900, Inada Naoki wrote:
> > On Mon, Jan 17, 2022 at 8:49 PM Steven D'Aprano <st...@pearwood.info>
> wrote:
> > >
> > > On Mon, Jan 17, 2022 at 08:04:50PM +0900, Inada Naoki wrote:
> > >
> > > > Name lookup is faster than building set in most case.
> > > > So I don't think cost to look name up is important at all.
> > >
> > > But the cost to look up the name is *in addition* to building the set.
> > >
> >
> > I meant it is negligible so we can just ignore it while this discussion.
>
> On my computer, the name lookup is almost a quarter of the time to build
> a set:
>
> [steve ~]$ python3.10 -m timeit "frozenset"
> 10000000 loops, best of 5: 24.4 nsec per loop
> [steve ~]$ python3.10 -m timeit "{1, 2, 3, 4, 5}"
> 2000000 loops, best of 5: 110 nsec per loop
>
> and about 10% of the total time:
>
> [steve ~]$ python3.10 -m timeit "frozenset({1, 2, 3, 4, 5})"
> 1000000 loops, best of 5: 237 nsec per loop
>
> If I use a tuple instead of the set, it is about 12% of the total time:
>
> [steve ~]$ python3.10 -m timeit "frozenset((1, 2, 3, 4, 5))"
> 2000000 loops, best of 5: 193 nsec per loop
>
> So not negligible.
>
> That is in the global scope, which will be much slower than a local scope.
Global builtins do a hash table lookup; local lookups just follow a
pointer.
>
>
>
> --
> Steve
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