What is the purpose of python's inner classes?

Question

Python\'s inner/nested classes confuse me. Is there something that can\'t be accomplished without them? If so, what is that thing?

Answer 1

Nesting classes within classes:

• Nested classes bloat the class definition making it harder to see whats going on.

• Nested classes can create coupling that would make testing more difficult.

• In Python you can put more than one class in a file/module, unlike Java, so the class still remains close to top level class and could even have the class name prefixed with an "_" to help signify that others shouldn't be using it.

The place where nested classes can prove useful is within functions

def some_func(a, b, c):
   class SomeClass(a):
      def some_method(self):
         return b
   SomeClass.__doc__ = c
   return SomeClass

The class captures the values from the function allowing you to dynamically create a class like template metaprogramming in C++