面向对象的多继承和super

Posted on | In |

单继承

定义父类Person

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class Person():
    def __init__(self, name, age):
        print('Person.__init__() 被调用')
        self.name = name
        self.age = age

    def eat(self, food):
        print(self.name, "正在吃{}".format(food))

使用super()调用父类的方法

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class YellowPeople(Person):
    def __init__(self, name, age, weight):
        print('YellowPeople.__init__() 被调用')
        # 调用父类（基类）的初始化两种方法__init__()
        # 1.直接使用父类名称调用，需要传入self
        # Person.__init__(self, name, age)
        # 2.使用super()调用
        super().__init__(name, age)
        self.weight = weight

    def print_some(self):
        print(self.name, '今年 {} 岁， 体重 {} 斤'.format(self.age, self.weight))

xiaoming = YellowPeople('xiaoming', 18, 110)
xiaoming.print_some()

直接使用父类的名称进行调用
与super()方式调用的区别是多传入了个self参数
可以看出使用super()方式调用更简洁

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class YellowPeople(Person):
    def __init__(self, name, age, weight):
        Person.__init__(self, name, age)
        self.weight = weight

    def print_some(self):
        print(self.name, '今年 {} 岁， 体重 {} 斤'.format(self.age, self.weight))

xiaoming = YellowPeople('xiaoming', 18, 110)
xiaoming.print_some()

可以看到init()的调用顺序：先子类，后父类

YellowPeople.init() 被调用
Person.init() 被调用
xiaoming 今年 18 岁， 体重 110 斤

多继承

同时继承多个父类

拥有所有父类的属性方法

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class Person():

    def __init__(self, name, age):
        print('Person.__init__() 被调用')
        self.name = name
        self.age = age

    def eat(self, food):
        print(self.name, "调用的是 Person 方法，正在吃{}".format(food))
		
class YellowPeopleFather(Person):
    def play(self):
        print('黄种人的 play 方法')

    def eat(self, food):
        print(self.name, '调用的是 YellowPeopleFather 方法， 正在吃{}'.format(food))
    pass

class WhitePeopleMother(Person):
    def say(self):
        print('白种人的 say 方法')

    def eat(self, food):
        print(self.name, '调用的是 WhitePeopleMother 方法， 正在吃{}'.format(food))
    pass

class son(YellowPeopleFather, WhitePeopleMother):
    def eat(self, food):
        print(self.name, '调用的是 son 方法，正在吃{}'.format(food))
    pass

# 查看类的__mro__属性，用于调用
print(son.__mro__)
xiaozhang = son('xiaozhang', 18)
xiaozhang.play()
xiaozhang.say()

(<class ‘main.son’>, <class ‘main.YellowPeopleFather’>, <class ‘main.WhitePeopleMother’>, <class ‘main.Person’>, <class ‘object’>)
Person.init() 被调用
黄种人的 play 方法
白种人的 say 方法

所有父子类都有相同的eat()方法，如何调用指定的类

son类本身就有eat方法，直接调用

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class son(YellowPeopleFather, WhitePeopleMother):
    def eat(self, food):
        print(self.name, '调用的是 son 方法，正在吃{}'.format(food))
    pass
	
xiaozhang = son('xiaozhang', 18)
xiaozhang.eat('food')

xiaozhang 调用的是 son 方法，正在吃food

调用YellowPeopleFather 类中的 eat 方法

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class son(YellowPeopleFather, WhitePeopleMother):
    def eat(self, food):
        super().eat('food')
    pass

xiaozhang 调用的是 YellowPeopleFather 方法， 正在吃food

调用WhitePeopleMother 类中的 eat 方法

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class son(YellowPeopleFather, WhitePeopleMother):
    def eat(self, food):
        super(YellowPeopleFather, self).eat('food')
    pass

xiaozhang 调用的是 WhitePeopleMother 方法， 正在吃food

调用Person 类(基类)中的 eat 方法

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class son(YellowPeopleFather, WhitePeopleMother):
    def eat(self, food):
        super(WhitePeopleMother, self).eat('food')
    pass

xiaozhang 调用的是 Person 方法，正在吃food

总结：super调用的本质是调用MRO顺序的下一个类，