Force child class to call parent method when overriding it

Question

I am curious whether there is a way in Python to force (from the Parent class) for a parent method to be called from a child class when it is being overridden.

Examp

Answer 1

If the class hierarchy is under your control, you can use what the Gang of Four (Gamma, et al) Design Patterns book calls the Template Method Pattern:

class MyBase:
   def MyMethod(self):
      # place any code that must always be called here...
      print "Base class pre-code"

      # call an internal method that contains the subclass-specific code
      self._DoMyMethod()

      # ...and then any additional code that should always be performed
      # here.
      print "base class post-code!"

   def _DoMyMethod(self):
      print "BASE!"


class MyDerived(MyBase):
   def _DoMyMethod(self):
      print "DERIVED!"


b = MyBase()
d = MyDerived()

b.MyMethod()
d.MyMethod()

outputs:

Base class pre-code
BASE!
base class post-code!
Base class pre-code
DERIVED!
base class post-code!