[Python-Dev] PEP 447 (type.__getdescriptor__)

[Nick Coghlan]

On 23 July 2015 at 03:12, Steve Dower <Steve.Dower at microsoft.com> wrote:
> Terry Reedy wrote:
>> On 7/22/2015 3:25 AM, Ronald Oussoren wrote:
>>> Hi,
>>>
>>> Another summer with another EuroPython, which means its time again to
>>> try to revive PEP 447…
>>>
>>> I’ve just pushes a minor update to the PEP and would like to get some
>>> feedback on this, arguably fairly esoteric, PEP.
>>
>> Yeh, a bit too esoteric for most of us to review. For instance, it is not
>> obvious to me, not familiar with internal details, after reading the intro, why
>> a custom __getattribute__ is not enough and why __getdescriptor__ would be
>> needed. If Guido does not want to review this, you need to find a PEP BDFL for
>> this.
>>
>> There are two fairly obvious non-esoteric questions:
>>
>> 1. How does this impact speed (updated section needed)?
>
> Agreed, this is important. But hopefully it's just a C indirection (or better yet, a null check) for objects that don't override __getdescriptor__.
>
>> 2. Is this useful, that you can think of, for anything other than connecting to
>> Objective C?
>
> There are other object models that would benefit from this, but I don't recall that we came up with uses other than "helps proxy to objects where listing all members eagerly is expensive and/or potentially incorrect". Maybe once you list all the operating systems that are now using dynamic object-oriented APIs rather than flat APIs (Windows, iOS, Android, ... others?) this is good enough?

"better bridging to other languages and runtimes" is a good enough
rationale for me, although I also wonder if it might be useful for
making some interesting COM and dbus based API wrappers.

Ronald, could you dig up a reference to the last thread (or threads)
on this? My recollection is that we were actually pretty happy with
it, and it was just set aside through lack of time to push it through
to completion.

Regards,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia