[Python-Dev] super() bug (?)

Guido van Rossum guido@python.org
Fri, 07 Mar 2003 14:42:12 -0500

> >>> class C(object):
> ...  def f(self): pass
> ...
> >>> class D(C): pass
> ...
> >>> D.f
> <unbound method D.f>
> >>> super(D,D).f
> <bound method D.f of <class '__main__.D'>>
> I think this should produce the same thing as D.f,

Really?  It makes no sense either way though.  super(D, D) only makes
sense from inside a class method; there the first argument should be
the current class and the second should be the cls argument to the
class method, e.g.:

  class C(object):
    def cm(cls): pass
    cm = classmethod(cm)

  class D(C):
    def cm(cls):
      super(D, cls).cm() # ~Same as C.cm(cls)

And this works.

I should also mention that super() should really only be used to call
a method with the same name as the currently called method -- I see
no use case for using super() with another method.

> that means implementation-wise
> f.__get__(None,D) should be called
> not f.__get__(D,D).
> _.__get__(None,D) would still do the right thing for static AND class methods:
> >>> def g(cls): pass
> ...
> >>> classmethod(g).__get__(None,D)
> <bound method type.g of <class '__main__.D'>>

It shouldn't be terribly hard to detect this situation and fix it
(somewhere in super_init()) but unless you have a use case I'd
rather consider this as a "don't care" situation.

--Guido van Rossum (home page: http://www.python.org/~guido/)