[Python-Dev] ABCs and MRO

[Terry Reedy]

Nick Coghlan wrote:
> Terry Reedy wrote:
>>>> As for the actual feature, I don't think it should hold up releases.
>>> Fair enough.
>> Given that the purpose of 2.7 is
>> a) maintenance of existing code (which can include minor new features
>> for existing facilities), and
>> b) easing conversion of code to 3.1
>> I am puzzled at the idea of adding a new facility to 2.7 that would not
>> be in 3.1+.  It would lock code into 2.7+ and counter purpose b).
> 
> It's possible we will end up in a situation where 3.0 and 3.1 are both
> aligned with 2.6, while 2.7 aligns with 3.2. That's particularly so with
> only 6 months or so between 3.0 and 3.1, while I currently expect the
> gap between 2.6 and 2.7 to be closer to the traditional 18 months.

OK, that suggests that the new feature should only be committed, if 
ever, to 2.7 after 3.1, when it can also be committed to 3.2 at the same 
time.