On Wed, Jul 19, 2017 at 5:20 PM, Tim Peters <tim.pet...@gmail.com> wrote:
> [Giampaolo Rodola' <g.rod...@gmail.com>]
> > Still much slower (-4.3x) than plain tuples though:
> >
> > $ python3.7 -m timeit -s "import collections; Point =>
> collections.namedtuple('Point', ('x', 'y'));" "Point(5, 11)"
> > 1000000 loops, best of 5: 313 nsec per loop
> >
> > $ python3.7 -m timeit "tuple((5, 11))"
> > 5000000 loops, best of 5: 71.4 nsec per loop
>
> I believe this was pointed out earlier: in the second case,
>
> 1. (5, 11) is built at _compile_ time, so at runtime it's only
> measuring a LOAD_FAST to fetch it from the code's constants block.
>
> 2. The tuple() constructor does close to nothing when passed a tuple:
> it just increments the argument's reference count and returns it.
>
> >>> t = (1, 2)
> >>> tuple(t) is t
> True
>
> In other words, the second case isn't measuring tuple _creation_ time
> in any sense: it's just measuring how long it takes to look up the
> name "tuple" and increment the refcount on a tuple that was created at
> compile time.
>
Oh right, I didn't realize that, sorry. Should have been something like
this instead:
$ python3.7 -m timeit -s "import collections; Point =
collections.namedtuple('Point', ('x', 'y')); x = [5, 1]" "Point(*x)"
1000000 loops, best of 5: 311 nsec per loop
$ python3.7 -m timeit -s "x = [5, 1]" "tuple(x)"
5000000 loops, best of 5: 89.8 nsec per loop
--
Giampaolo - http://grodola.blogspot.com
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