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

[Mark Shannon]

Hi,

On 22/07/15 09:25, Ronald Oussoren wrote:> Hi,
> 
> Another summer with another EuroPython, which means its time again to 
> try to revive PEP 447…
> 

IMO, there are two main issues with the PEP and implementation.

1. The implementation as outlined in the PEP is infinitely recursive, since the
lookup of "__getdescriptor__" on type must necessarily call
type.__getdescriptor__.
The implementation (in C) special cases classes that inherit "__getdescriptor__"
from type. This special casing should be mentioned in the PEP.

2. The actual implementation in C does not account for the case where the class
of a metaclass implements __getdescriptor__ and that method returns a value when
called with "__getdescriptor__" as the argument.



Why was "__getattribute_super__" rejected as an alternative? No reason is given.

"__getattribute_super__" has none of the problems listed above.
Making super(t, obj) delegate to t.__super__(obj) seems consistent with other
builtin method/classes and doesn't add corner cases to the already complex
implementation of PyType_Lookup().

Cheers,
Mark