[Python-Dev] Add __reversed__ methods for dict

[Guido van Rossum]

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
>
> .
>
> _______________________________________________
> 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)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20180525/201eb327/attachment-0001.html>