[Python-Dev] PEP 487: Simpler customization of class creation

Martin Teichmann lkb.teichmann at gmail.com
Thu Jun 16 17:17:14 EDT 2016

Hi Eric, hi List,

> I'd be glad to give feedback on this, probably later today or
> tomorrow.  In particular, I'd like to help resolve the intersection
> with PEP 520. :)

Thanks in advance! Let me already elaborate on the differences, so
that others can follow:

You chose the name "__definition_order__", I chose
"__attribute_order__", I am fine with either, what are other people's

The bigger difference is actually the path to inclusion into Python:
my idea is to first make it a standard library feature, with the later
option to put it into the C core, while you want to put the feature
directly into the C core. Again I'm fine with either, as long as the
feature is eventually in.

As a side note, you propose to use OrderedDict as the class definition
namespace, and this is exactly how I implemented it. Nonetheless, I
would like to keep this fact as an implementation detail, such that
other implementations of Python (PyPy comes to mind) or even CPython
at a later time may switch to a different way to implement this
feature. I am thinking especially about the option to determine the
-_order__ already at compile time. Sure, this would mean that someone
could trick us by dynamically changing the order of attribute
definition, but I would document that as an abuse of the functionality
with undocumented outcome.



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