Question

I saw an example today of a method overriding a method in a base class that had a different name, how and why is this possible? And what uses could it possibly have?

>>> class A(object):
...   def foo(self):
...     self.__bar()
...   def __bar(self):
...     print "original"
... 
>>> class B(A):
...   def _A__bar(self):
...     print "overridden"
... 
>>> B().foo()
overridden

Answer 1

Wow, that is really horrible.

This works because methods that begin with a double-underscore – the __bar method in A – are name-mangled as a very basic way of simulating “private” functions in Python. But they’re not actually private, they’re just prefixed with _classname. So the coder here is taking advantage of this to override the so-called private method in A.

This works, but you shouldn’t ever do it. (In fact, you should almost never use the double-underscore private attributes anyway, but that’s a different discussion.)