Automatically decorate superclass functions in subclass?

Question

I have a subclass that adds graphics capabilities to a superclass that implements the algorithms. So, in addition to a few extra initialization functions, this subclass will only need to refresh the graphics after the execution of each algorithm-computing function in the superclass.

Classes:

class graph(algorithms):
  ... #initialization and refresh decorators

  @refreshgraph
  def algorithm1(self, *args, **kwargs):
    return algorithms.algorithm1(self, *args, **kwargs)

  @refreshgraph
  def algorithm2(self, *args, **kwargs):
    return algorithms.algorithm2(self, *args, **kwargs)

  ... #and so on

Is there an pythonic way to automatically decorate all the non-private methods defined in the superclass, such that if I add a new algorithm there I don't need to explicitly mention it in my subclass? I would also like to be able to explicitly exclude some of the superclass' methods.

Answer 1

The subclass always gets all the methods from the parent class(es) by default. If you wish to make emulate the behavior other languages use for privacy (eg the 'private' or 'protected' modifiers in C#) you have two options:

1) Python convention (and it's just a convention) is that methods with a single leading underscore in their names are not designed for access from outside the defining class.

2) Names with a double leading underscore are mangled in the bytecode so they aren't visible to other code under their own names. ParentClass.__private is visible inside ParentClass, but can only be accessed from outside ParentClass as ParentClass._ParentClass__private. (Great explanations here). Nothing in Python is truly private ;)

To override an inherited method just define the same name in a derived class. To call the parent class method inside the derived class you can do it as you did in your example, or using super:

def algorithm2(self, *args, **kwargs):
  super(graph, self).algorithm2(self, *args, **kwargs)
  # do other derived stuff here....
  self.refresh()