On Wed, Jul 8, 2020 at 7:13 PM Inada Naoki <[email protected]> wrote:
> I think this comparison is unfair.
>
well, benchmarks always lie ....
> > d.items()[0] vs list(d.items())[0]
>
> Should be compared with `next(iter(d.items())`
>
why? the entire point of this idea is to have indexing syntax -- we can
already use the iteration protocol top do this. Not that it's a bad idea to
time that too, but since under the hood it's doing the same or less work,
I'm not sure what the point is.
> d.keys()[-1] vs list(d.keys())[-1]
>
> Should be compared with `next(reversed(d.keys()))`, or `next(reversed(d))`.
>
Same point - the idea is to have indexing syntax. Though yes, it would be
good to see how it compares. But I know predicting performance is usually
wrong, but this is going to require a full traversal of the underlying keys
in either case.
> > random.choice(d.items()) vs random.choice(list(d.items()))
>
> Should be compared with `random.choice(items_list)` with `items_list =
> list(d.items())` setup too.
>
I don't follow this one -- could you explain? what is items_list ?
But what this didn't check is how bad the performance could be for what I
expect would be a bad performance case -- indexing teh keys repeatedly:
for i in lots_of_indexes:
a_dict.keys[i]
vs:
keys_list = list(a_dict.keys)
for it in lots_of_indexes:
keys_list[i]
I suspect it wouldn't take all that many indexes for making a list a better
option.
But again, we are badk to use cases. As Stephen pointed out no one has
produced an actualy production code use case.
I myself have wanted this (the random.choice option) -- but it wasn't
production code it was a learning exercise, specifically:
http://codekata.com/kata/kata14-tom-swift-under-the-milkwood/
I can imagine there would be that use case in real world code, but I
haven't had it.
-CHB
>
> --
> Inada Naoki <[email protected]>
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--
Christopher Barker, PhD
Python Language Consulting
- Teaching
- Scientific Software Development
- Desktop GUI and Web Development
- wxPython, numpy, scipy, Cython
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