why.py

class Class1:
  def __init__(self, arg1, arg2):
    print "Would do stuff with %s and %s" % (arg1, arg2)

class Class2(Class1):
  def do_something(self):
    print "I would do something else"

class Class3(Class1):
  def __init__(self, arg1, arg2):
    Class1.__init__(self, arg1, arg2)
  
  def do_something(self):
    print "I would do something else"