On 9/10/2016 5:27 AM, Nick Coghlan wrote:
On 10 September 2016 at 17:49, Ethan Furman <et...@stoneleaf.us> wrote:
Per Victor's advice I'm posting this here.
PEP 520 has been accepted, but without the __definition_order__ attribute.
The accompanying comment:
"Note: Since compact dict has landed in 3.6, __definition_order__ has
been removed. cls.__dict__ now mostly accomplishes the same thing
instead."
The "mostly" is what concerns me. Much like having a custom __dir__ lets
a class fine-tune what is of interest, a custom __definition_order__ allows
a class to present a unified view of the class creation process. This could
be important to classes that employ __getattr__ (or __getattribute__) to
provide virtual attributes, such as Enum or proxy classes.
+1
The reasoning for modifying the PEP post-acceptance is faulty -
__definition_order__ wasn't just there as a CPython implementation
detail, it was there as a way to allow class and metaclass developers
to hide their *own* irrelevant implementation details.
Since __definition_order__ was already accepted, and the rationale for
removing it is incorrect, could we please have it back for beta 1?
Someone (Ethan?) should ask that this be a release blocker on some issue.
--
Terry Jan Reedy
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