[Python-Dev] Guarantee ordered dict literals in v3.7?

[INADA Naoki]

Hi, folks.

TLDR, was the final decision made already?

If "dict keeps insertion order" is not language spec and we
continue to recommend people to use OrderedDict to keep
order, I want to optimize OrderedDict for creation/iteration
and memory usage.  (See https://bugs.python.org/issue31265#msg301942 )

If dict ordering is language spec, I'll stop the effort and
use remaining time to another optimizations.

My thought is, +1 to make it language spec.

* PHP (PHP 7.2 interpreter is faster than Python) keeps insertion order.
  So even we make it language spec, I think we have enough room
  to optimize.

* It can make stop discussion like "Does X keeps insertion order?
  It's language spec?", "What about Y? Z?".  Everything on top of dict
  keeps insertion order.  It's simple to learn and explain.

Regards,
INADA Naoki  <songofacandy at gmail.com>


On Sun, Nov 5, 2017 at 3:35 AM, Guido van Rossum <guido at python.org> wrote:
> This sounds reasonable -- I think when we introduced this in 3.6 we were
> worried that other implementations (e.g. Jython) would have a problem with
> this, but AFAIK they've reported back that they can do this just fine. So
> let's just document this as a language guarantee.
>
> On Sat, Nov 4, 2017 at 10:30 AM, Stefan Krah <stefan at bytereef.org> wrote:
>>
>>
>> Hello,
>>
>> would it be possible to guarantee that dict literals are ordered in v3.7?
>>
>>
>> The issue is well-known and the workarounds are tedious, example:
>>
>>
>> https://mail.python.org/pipermail/python-ideas/2015-December/037423.html
>>
>>
>> If the feature is guaranteed now, people can rely on it around v3.9.
>>
>>
>>
>> Stefan Krah
>>
>>
>>
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>
>
>
> --
> --Guido van Rossum (python.org/~guido)
>
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