《笨办法学Python》笔记32-----对象、类以及从属关系

对象、类

类就像一套印钱的模具，对象就是用这套模具印出来的钞票。

类的关系---继承

就像儿子继承父亲的家产，儿子可以少奋斗10年。子类继承父类後，可以获得父类的属性和方法，子类可以省去重复部分代码。

教材举例

class Animal(object):
    pass

class Dog(Animal):
    def __init__(self, name):
        print "Dog class init"
        self.name = name

class Cat(Animal):
    def __init__(self, name):
        print "Cat class init"
        self.name = name

class Person(object):
    def __init__(self, name):
        print "Person class init"
        print "person super"
        self.name = name
        self.pet = None

class Employee(Person):
    def __init__(self, name, salary):
        print "Employee class init"
        super(Employee, self).__init__(name)
        self.salary = salary

class Fish(object):
    pass

class Salmon(Fish):
    pass

class Halibut(Fish):
    pass

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()

这段代码定义了8个类，包括

-动物类(Animal)

----猫类(Cat)

----狗类(Dog)

-人类(Person)

----职员类(Employee)

-鱼类(Fish)

----三文鱼类(Salmon)

----大比目鱼类(Halibut)

这里的父类子类在现实中也是有意义的，比如猫和狗都属于动物，职员是一个人，三文鱼和比目鱼都是鱼。

init是类的初始化方法，在实例化时（用模板印钞票时）会自动调用这个构造函数。

注意Employee类的构造函数中有一句代码“super(Employee, self).init(name)”

查询帮助文档

super(type[, object-or-type])
Return a proxy object that delegates method calls to a parent or sibling class of type. This is useful for accessing inherited methods that have been overridden in a class. The search order is same as that used by getattr() except that the type itself is skipped.

super是一个类，“super(Employee, self)”调用了super的初始化方法，返回一个能调用父类或兄弟类的代理对象，用于访问在一个类中被重写的继承方法非常有用。可以参考一下链接了解。

详解类的继承