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From: Robert Kern <robert.kern@gmail.com>
Subject: Re: Problems with subclassing enum34
Date: Fri, 28 Jun 2013 12:16:40 +0100
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Xref: csiph.com comp.lang.python:49370

On 2013-06-28 11:48, Thomas Heller wrote:
> trying out the enum34 module.
>
> What I want to create is a subclass of enum.Enum that is also
> based on ctypes.c_int so that I can better use enum instances
> in ctypes api calls.
>
> When I do this, I get a metaclass conflict:
>
>
>  >>> class MyEnum(ctypes.c_int, enum.Enum):
> ...    FOOBAR = 0
> ...
> Traceback (most recent call last):
>    File "<stdin>", line 1, in <module>
> TypeError: Error when calling the metaclass bases
>      metaclass conflict: the metaclass of a derived class must be a (non-strict)
> subclass of the metaclasses of all its bases
>  >>>
>
>
>
> When I do this, it does not work either:
>
>  >>> class MyEnum_meta(type(ctypes.c_int), type(enum.Enum)):
> ...     pass

enum.EnumMeta uses super() in its __new__() implementation but 
_ctypes.PyCSimpleType doesn't. Thus, only _ctypes.PyCSimpleType.__new__() gets a 
chance to run. Switching the order of the two might work.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco