Using inheritance to simplify class definitions

We can use inheritance—reuse of code from a superclass in subclasses—which can simplify a subclass definition. In an earlier example, we created the MyAppError class as a subclass of Exception. This means that all of the features of Exception will be available to MyAppError. This works because of the three-step search for a name: if a method name is not found in an object's class, then the superclasses are all searched for the name.

Here's an example of a subclass which overrides just one method of the parent class:

class Manhattan_Point(Point):
    def dist(self, point):
        return abs(self.x-point.x)+abs(self.y-point.y)

We've defined a subclass of Point named Manhattan_Point. This class has all of the features of a Point. It makes a single change to the parent class. It provides a definition for the dist() method that will override the definition in the Point superclass.

Here's an example that shows how...