super() fails with error: TypeError “argument 1 must be type, not classobj” when parent does not inherit from object

Your problem is that class B is not declared as a “new-style” class. Change it like so:

class B(object):

and it will work.

super() and all subclass/superclass stuff only works with new-style classes. I recommend you get in the habit of always typing that (object) on any class definition to make sure it is a new-style class.

Old-style classes (also known as “classic” classes) are always of type classobj; new-style classes are of type type. This is why you got the error message you saw:

TypeError: super() argument 1 must be type, not classobj

Try this to see for yourself:

class OldStyle:
    pass

class NewStyle(object):
    pass

print type(OldStyle)  # prints: <type 'classobj'>

print type(NewStyle) # prints <type 'type'>

Note that in Python 3.x, all classes are new-style. You can still use the syntax from the old-style classes but you get a new-style class. So, in Python 3.x you won’t have this problem.