class - How to detect method overloading in subclasses in python?

Question

I have a class that is a super-class to many other classes. I would like to know (in the init() of my super-class if the subclass has overridden a specific method.

I tried to accomplish this with a class method, but the results were wrong:

class Super:
   def __init__(self):
      if self.method == Super.method:
         print 'same'
      else:
         print 'different'

   @classmethod
   def method(cls):
      pass

class Sub1(Super):
   def method(self):
      print 'hi'

class Sub2(Super):
   pass

Super() # should be same
Sub1() # should be different
Sub2() # should be same

>>> same
>>> different
>>> different

Is there any way for a super-class to know if a sub-class has overridden a method?

Answer 1

You can use your own decorator. But this is a trick and will only work on classes where you control the implementation.

def override(method):
  method.is_overridden = True
  return method

class Super:
   def __init__(self):
      if hasattr(self.method, 'is_overridden'):
         print 'different'
      else:
         print 'same'
   @classmethod
   def method(cls):
      pass

class Sub1(Super):
   @override
   def method(self):
      print 'hi'

class Sub2(Super):
   pass

Super() # should be same
Sub1() # should be different
Sub2() # should be same

>>> same
>>> different
>>> same