[Python-Dev] Python 3.6 dict becomes compact and gets a private version; and keywords become ordered

[Chris Angelico]

On Sun, Sep 11, 2016 at 6:42 PM, Victor Stinner
<victor.stinner at gmail.com> wrote:
> 2016-09-10 23:24 GMT-04:00 Nick Coghlan <ncoghlan at gmail.com>:
>> To conform with the updated language spec, implementations just need
>> to use collections.OrderedDict in 3 places:
>>
>> (...)
>> - storage type for passing kwargs to functions
>
> I'm not sure about the "just need" for this one, especially if you
> care of performances ;-)
>
> I mean, it's not easy to write an *efficient* hash table preserving
> the insertion order. Otherwise, CPython would have one since Python
> 1.5 :-)

Can the requirement for kwargs be weakened to "preserves insertion
order as long as it is not mutated"? That might make it easier on
implementations.

ChrisA