What is a basic example of single inheritance using the super() keyword in Python?

Question

Let's say I have the following classes set up:

class Foo:      def __init__(self, frob, frotz):           self.frobnicate = frob           self.frotz = frotz class Bar:      def __init__(self, frob, frizzle):           self.frobnicate = frob           self.frotz = 34           self.frazzle = frizzle 

How can I (if I can at all) use super() in this context to eliminate the duplicate code?

Answer 1

Assuming you want class Bar to set the value 34 within its constructor, this would work:

class Foo(object):      def __init__(self, frob, frotz):           self.frobnicate = frob           self.frotz = frotz  class Bar(Foo):      def __init__(self, frob, frizzle):           super(Bar, self).__init__(frob, frizzle)           self.frotz = 34           self.frazzle = frizzle   bar = Bar(1,2) print "frobnicate:", bar.frobnicate print "frotz:", bar.frotz print "frazzle:", bar.frazzle 

However, super introduces its own complications. See e.g. super considered harmful. For completeness, here's the equivalent version without super.

class Foo(object):      def __init__(self, frob, frotz):           self.frobnicate = frob           self.frotz = frotz  class Bar(Foo):      def __init__(self, frob, frizzle):           Foo.__init__(self, frob, frizzle)           self.frotz = 34           self.frazzle = frizzle   bar = Bar(1,2) print "frobnicate:", bar.frobnicate print "frotz:", bar.frotz print "frazzle:", bar.frazzle 

Answer 2

In Python >=3.0, like this:

class Foo():     def __init__(self, frob, frotz)         self.frobnicate = frob         self.frotz = frotz  class Bar(Foo):     def __init__(self, frob, frizzle)         super().__init__(frob, 34)         self.frazzle = frizzle 

Read more here: http://docs.python.org/3.1/library/functions.html#super

EDIT: As said in another answer, sometimes just using Foo.__init__(self, frob, 34) can be the better solution. (For instance, when working with certain forms of multiple inheritance.)