[Tutor] error message with multiple inheritance

[simone]

Christopher Spears ha scritto:

> I've been working out of Core Python Programming (2nd Edition).  Here is an example demonstrating multiple inheritance.
> 
>>>> class A(object):
> ...     pass
> ...
>>>> class B(A):
> ...     pass
> ...
>>>> class C(B):
> ...     pass
> ...
>>>> class D(A, B):
> ...     pass
> ...
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: Error when calling the metaclass bases
>     Cannot create a consistent method resolution
> order (MRO) for bases B, A
> 
> What does this error message mean?  The example worked in the book.  I checked in the docs and could not find anything.

http://www.python.org/download/releases/2.3/mro/
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