Question

In Python 2.5, the following code raises a TypeError:

>>> class X:       def a(self):         print 'a'  >>> class Y(X):       def a(self):         super(Y,self).a()         print 'b'  >>> c = Y() >>> c.a() Traceback (most recent call last):   File '<stdin>', line 1, in <module>   File '<stdin>', line 3, in a TypeError: super() argument 1 must be type, not classobj 

If I replace the class X with class X(object), it will work. What’s the explanation for this?

Answer 1

The reason is that super() only operates on new-style classes, which in the 2.x series means extending from object:

>>> class X(object):         def a(self):             print 'a'  >>> class Y(X):         def a(self):             super(Y, self).a()             print 'b'  >>> c = Y() >>> c.a() a b