ex42.py

## Animal is-a object
class Animal(object):
    pass

## Dog is-a Animal
class Dog(Animal):

    def __init__(self, name):
        ## Dog has-a name
        self.name = name

## Cat is-a Animal
class Cat(Animal):

    def __init__(self, name):
        ## Cat has-a name
        self.name = name

## Person is-a object
class Person(object):

    def __init__(self, name):
        ## Person has-a name
        self.name = name

        ## Person has-a pet of some kind
        self.pet = None

## Employee is-a Person
class Employee(Person):

    def __init__(self, name, salary):
        ## Employee has-a name
        super(Employee, self).__init__(name)
        ## Employee has-a salary
        self.salary = salary

## Fish is-a object
class Fish(object):
    def blubb(self):
        print "Blubb, blubb!"

## Salmon is-a Fish
class Salmon(Fish):
    def hello(self):
        print "Hello, I'm a salmon!"

## Halibut is-a Fish
class Halibut(Fish):
    pass


## rover is-a Dog
rover = Dog("Rover")
print rover.name

## satan is-a Cat
satan = Cat("Satan")

## mary is-a Person
mary = Person("Mary")

## mary has-a satan
mary.pet = satan
print "Mary's pet's name is:", mary.pet.name

## frank is-a Employee
frank = Employee("Frank", 120000)

## frank has-a rover
frank.pet = rover

## flipper is-a Fish
flipper = Fish()

## crouse is-a Salmon
crouse = Salmon()
crouse.blubb()
crouse.hello()

## harry is-a Halibut
harry = Halibut