Stateful Objects use Mix-ins to define behaviour

You want to implement stateful objects, which have a different set of behaviours according to what state they are in. This requirement can be achieved with the use of mix-ins. A mix-in is a class which is dynamically inherited by an object. The methods of the mix-in class are thus accessible through the object. This is a clean way of providing objects with standard Interfaces. Chuck Esterbrook has written a discussion of mix-ins, and their implementation in Python. The recipe draws from the Famous "Lumberjack Song". If you`re not familiar with it, all you need to know is that the Passage Of Time modifies the Lumberjack`s behaviour.