Exercise 42: Is-A, Has-A, Objects, and Classes

## Animal is-a object (yes, sort of confusing) look at the extra credit
class Animal(object):
　　pass
## ??
class Dog(Animal):
　　def __init__(self, name): ## ??
　　　　self.name = name
## ??
class Cat(Animal):
　　def __init__(self, name): ## ??
　　　　self.name = name
## ??
class Person(object):
　　def __init__(self, name): ## ??
　　　　self.name = name
## Person has-a pet of some kind
　　self.pet = None
## ??
class Employee(Person):
　　def __init__(self, name, salary): ## ?? hmm what is this strange magic?
　　　　super(Employee, self).__init__(name) ## ??
　　　　self.salary = salary
## ??
class Fish(object):
　　pass
## ??
class Salmon(Fish):
　　pass
## ??
class Halibut(Fish):
　　pass
## rover is-a Dog
rover = Dog("Rover")
## ??
satan = Cat("Satan")
## ??
mary = Person("Mary")
## ??
mary.pet = satan
## ??
frank = Employee("Frank", 120000)
## ??
frank.pet = rover
## ??
flipper = Fish()
## ??
crouse = Salmon()
## ??
harry = Halibut()