Inheritance is a

mechanism

  whereby one class can be derived from a base-class allowing us to make behavior more specific in the subclass. In nominally typed languages such as Java, class-based inheritance is the means by which run-time polymorphism is achieved. Not so in Python, as we have just demonstrated. The fact that no Python method calls or attribute lookups are bound to actual objects until the point at which they are called – known as late-binding – means we can attempt polymorphism with any object and it will succeed if the object fits.

Although inheritance in Python can be used to facilitate polymorphism – after all, derived classes will have the same interfaces as base classes – inheritance in Python is most useful for sharing implementation between classes.