[Python-Dev] Classes and Metaclasses in Smalltalk

[Thomas Heller]

> thomas wrote:
> 
> > > why not spell it out:
> > > 
> > >     self.__super__.foo(arg1, arg2)
> > > 
> > > or
> > > 
> > >     self.super.foo(arg1, arg2)
> > > 
> > > or
> > > 
> > >     super(self).foo(arg1, arg2)
> >
> > IMO we still need to specify the class, and there we are:
> > 
> >      super(self, MyClass).foo(arg1, arg2)
> 
> isn't that the same as self.__class__ ?  in which case
> super is something like:
> 
> import new
> 
> class super:
>     def __init__(self, instance):
>         self.instance = instance
>     def __getattr__(self, name):
>         for klass in self.instance.__class__.__bases__:
>             member = getattr(klass, name, None)
>             if member:
>                 if callable(member):
>                     return new.instancemethod(member, self.instance, klass)
>                 return member
>         raise AttributeError(name)
> 
No, it's not the same. Consider:

class X:
    def test(self):
        print "test X"

class Y(X):
    def test(self):
        print "test Y"
        super(self).test()

class Z(Y):
    pass
        
X().test()
print
Y().test()
print
Z().test()
print

This prints:
test X

test Y
test X

test Y
test Y
(more test Y lines deleted)
Runtime error: maximum recursion depth exceeded

This is because super(self).test for the Z() object
should start the search in the X class, not in the Y class.


Thomas