[Python-Dev] Add __reversed__ methods for dict

[Ramsey D'silva]

I am also in agreement.

On Fri, May 25, 2018, 13:49 Guido van Rossum <guido at python.org> wrote:

> OK, +1
>
> On Fri, May 25, 2018 at 10:26 AM, Raymond Hettinger <
> raymond.hettinger at gmail.com> wrote:
>
>>
>>
>> > On May 25, 2018, at 9:32 AM, Antoine Pitrou <solipsis at pitrou.net>
>> wrote:
>> >
>> > It's worth nothing that OrderedDict already supports reversed().
>> > The argument could go both ways:
>> >
>> > 1. dict is similar to OrderedDict nowadays, so it should support
>> >   reversed() too;
>> >
>> > 2. you can use OrderedDict to signal explicitly that you care about
>> >   ordering; no need to add anything to dict.
>>
>> Those are both valid sentiments :-)
>>
>> My thought is that guaranteed insertion order for regular dicts is brand
>> new, so it will take a while for the notion settle in and become part of
>> everyday thinking about dicts.  Once that happens, it is probably
>> inevitable that use cases will emerge and that __reversed__ will get added
>> at some point.  The implementation seems straightforward and it isn't much
>> of a conceptual leap to expect that a finite ordered collection would be
>> reversible.
>>
>> Given that dicts now track insertion order, it seems reasonable to want
>> to know the most recent insertions (i.e. looping over the most recently
>> added tasks in a task dict).  Other possible use cases will likely
>> correspond to how we use the Unix tail command.
>>
>> If those use cases arise, it would be nice for __reversed__ to already be
>> supported so that people won't be tempted to implement an ugly workaround
>> using popitem() calls followed by reinsertions.
>>
>>
>> Raymond
>>
>> .
>>
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>
>
>
> --
> --Guido van Rossum (python.org/~guido)
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