Le lundi 26 juin 2006 20:06, [EMAIL PROTECTED] a écrit :
> What are the reason one would get this error: TypeError: Cannot create
> a consistent method resolution order (MRO) for bases object ??
>
> I can provide the code if needed....
This is the python solution to the diamond problem (cf. wikipedia).
In [61]: class a(object) : pass
....:
In [62]: class b(a) : pass
....:
In [63]: class c(object, a) : pass
....:
---------------------------------------------------------------------------
exceptions.TypeError Traceback (most recent
call last)
/home/maric/<ipython console>
TypeError: Error when calling the metaclass bases
Cannot create a consistent method resolution
order (MRO) for bases object, a
In [64]: b.mro()
Out[64]: [<class '__main__.b'>, <class '__main__.a'>, <type 'object'>]
In [65]: class c(a, object) : pass
....:
In [66]: c.mro()
Out[66]: [<class '__main__.c'>, <class '__main__.a'>, <type 'object'>]
In [67]: class d(b, c) : pass
....:
In [69]: d.mro()
Out[69]:
[<class '__main__.d'>,
<class '__main__.b'>,
<class '__main__.c'>,
<class '__main__.a'>,
<type 'object'>]
mro means "method resolution order", this is the path the interpreter will
look for attributes for a given class. You cannot introduce inconsistency in
this path, for example duplicate the type object before another type (or any
type wich appear to be the ancestor of another).
--
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Maric Michaud
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