[Python-ideas] factory for efficient creation of many dicts with the same keys

[Guido van Rossum]

I think you've got it backwards -- if you send the patch the idea *may* be
accepted. You ought to at least show us the docs for your proposed factory,
it's a little murky from your example.

On Fri, Sep 8, 2017 at 6:34 AM, Sergey Fedoseev <fedoseev.sergey at gmail.com>
wrote:

> Hi all,
>
> Sometimes you may need to create many dicts with the same keys, but
> different
> values. For example, if you want to return data from DB as dicts.
>
> I think that special type could be added to solve this task more
> effectively.
> I created proof of concept for this and here's benchmarks:
>
> # currently the fastest way to do it AFAIK
> $ ./python -m timeit -s "nkeys = 5; nrows = 1000; rows = [(i,)*nkeys
> for i in range(nrows)]; enumerated = list(enumerate(range(nkeys)))"
> "for row in rows: {key: row[i] for i, key in enumerated}"
> 500 loops, best of 5: 645 usec per loop
>
> $ ./python -m timeit -s "nkeys = 5; nrows = 1000; rows = [(i,)*nkeys
> for i in range(nrows)]; factory = dict.factory(*range(nkeys)); from
> itertools import starmap" "for d in starmap(factory, rows): d"
> 5000 loops, best of 5: 81.1 usec per loop
>
> I'd like to write a patch if this idea will be accepted.
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-- 
--Guido van Rossum (python.org/~guido)
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