[Python-Dev] Add __reversed__ methods for dict

[Guido van Rossum]

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
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-- 
--Guido van Rossum (python.org/~guido)
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