Override and extend

- [Instructor] Now that we understand the basics…of class inheritance,…I want to talk more about overriding and extending.…These are the main reasons…that we want to create subclasses.…I mean, obviously, we want to inherit a lot of the behaviors…of the parent class,…but on it's own, that's not enough.…Otherwise, we just have a new class…that acts exactly like the parent.…Overriding and extending is what allows us to modify…those behaviors so they can't be unique to the subclass.…We either override behaviors which we want to perform…differently in the subclass,…or we add new behaviors in the subclass…that the parent doesn't have.…

And that's extending.…Let me give you an example in code.…Let's say that we have a parent class called Sofa.…It has a class attribute called can_open…which is set to false.…And I've got an attribute accessor…for the width and the length.…And I've also got a method called area…which returns the area of the sofa.…The idea being the amount of space…it takes up on a floor plan.…So it's the width times the length…