[Python-Dev] Add __reversed__ methods for dict

[Guido van Rossum]

(Also this probably belongs in python-ideas, unless there's already a
bugs.python.org issue for it -- but you didn't mention that so I assume
it's just an idea? How did you reach the line count estimates?)

On Fri, May 25, 2018 at 8:46 AM, Guido van Rossum <guido at python.org> wrote:

> Please go find some real world code that would benefit from this. Don't
> make up examples, just show some code in a repository (public if possible,
> but private is okay, as long as you can quote small amounts of code from
> it) where te existence of reverse iteration over a dict would have been
> helpful.
>
> On Thu, May 24, 2018 at 5:55 AM, Rémi Lapeyre <remi.lapeyre at vint.fr>
> wrote:
>
>>
>> Hi,
>>
>> since dict keys are sorted by their insertion order since Python 3.6 and
>> that
>> it’s part of Python specs since 3.7 a proposal has been made in bpo-33462
>> to
>> add the __reversed__ method to dict and dict views.
>>
>> Concerns have been raised in the comments that this feature may add too
>> much
>> bloat in the core interpreter and be harmful for other Python
>> implementations.
>>
>> Given the different issues this change creates, I see three possibilities:
>>
>> 1. Accept the proposal has it is for dict and dict views, this would add
>> about
>> 300 lines and three new types in dictobject.c
>>
>> 2. Accept the proposal only for dict, this would add about 80 lines and
>> one
>> new type in dictobject.c while still being useful for some use cases
>>
>> 3. Drop the proposal as the whole, while having some use,
>> reversed(dict(a=1, b=2))
>> may not be very common and could be done using OrderedDict instead.
>>
>> What’s your stance on the issue ?
>>
>> Best regards,
>> Rémi Lapeyre
>> _______________________________________________
>> Python-Dev mailing list
>> Python-Dev at python.org
>> https://mail.python.org/mailman/listinfo/python-dev
>> Unsubscribe: https://mail.python.org/mailman/options/python-dev/guido%
>> 40python.org
>>
>
>
>
> --
> --Guido van Rossum (python.org/~guido)
>



-- 
--Guido van Rossum (python.org/~guido)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20180525/dc3b0c01/attachment.html>