solving the metaclass conflict

[David Mertz]

mis6 at pitt.edu (Michele Simionato) wrote previously:
|> Of course:
|>     M = _generatemetaclass((),(A,B,C),0)
|>     #-> TypeError: MRO conflict among bases B, C, A
|> Which is a bad thing.  Is that the real concern?

|Of course not, since this is an issue with the C3 method resolution
|order (http://www.python.org/2.3/mro.html) which in principle has
|nothing to do with metaclasses.

Yes and no.  I know that MRO conflicts don't have anything to do with
metaclasses per se.  But if a version of _generatemetaclass() happened
to remove all the extraneous superclasses from the metabases tuple, that
would make many (all?) MRO conflicts do away.

I think removing those extra superclasses would be a good thing.  But I
don't feel strongly; and there might be some reason I have overlooked
why it wouldn't be so good.

|class C(object,type): pass
|gives a MRO conflict (under Python 2.3).

Hmmm... actually, the question never came to my mind.  I'm not sure what
my first guess would have been--especially since, as you hint, Python
2.2 behaves differently.  Just a little more for readers:

  class C(type, object): pass

Is perfectly happy under both 2.2 and 2.3.  Again, obvious to Michele,
but probably not to some other readers.

Yours, David...

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