python3多继承 __init__ python多继承 super

一、其实，“类只是一个结构”，它并不是实例化出来的对象了，只是定义，那么在定义方法的时候想要用到 super 类的方法，你就只能用 super或者用类名来调用它。

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

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


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

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


handsomeb = YellowPeople('liyuanchao', 21, 120)
handsomeb.print_some()

运行结果如下：

接下来给你讲的多继承，相信你会对 super 更近一步的认识。来举一个多继承的例子：

借用一张图

按照上图我们可以写出以下代码

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

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


class YellowPeopleFather(Person):
    def yellow_say(self):
        print('this is yellow people method')


class WhitePersonMother(Person):
    def white_say(self):
        print('this is white people method')


class Son(YellowPeopleFather, WhitePersonMother):
    pass
test=Son('liyuanchao',18)
test.yellow_say()
test.white_say()

YellowPeopleFather(Person) 和 WhitePersonMother(Person) 是单继承，而 class Son(YellowPeopleFather, WhitePersonMother) 同时继承了 YellowPeopleFather 和 WhitePersonMother ，即就是多继承，实例化出 Son 对象的时候，可以同时拥有 YellowPeopleFather 和 WhitePersonMother 的东西，运行结果如下：

当父类都拥有共同的方法如何调用呢：

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

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


class YellowPeopleFather(Person):
    def eat(self):
        print('this is yellow people method')


class WhitePersonMother(Person):
    def eat(self):
        print('this is white people method')


class Son(YellowPeopleFather, WhitePersonMother):
    pass
test=Son('liyuanchao',18)
test.eat()

运行结果如下：

可以看到调用的是YellowPeopleFather类中的eat方法，这时候我们就要理解多重继承的子类，调用方法的顺序了，在 Python 中，使用到的是 MRO（这里不做过多解释了） ，我们可以通过调用子类的 mro 方法来具体查看，运行结果如下：

可以看到，这里是调用的顺序是：Son->YellowPeopleFather–>WhitePersonMother–>Person–>object。

• 没有在Son类中定义eat方法，所有优先在YellowPeopleFather类中寻找是否有eat方法，如果没有继续往后寻找。
  其实调用 super 的时候，其实是调用 MRO 顺序的下一个类。

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

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


class YellowPeopleFather(Person):
    def eat(self):
        print('this is yellow people method')


class WhitePersonMother(Person):
    def eat(self):
        print('this is white people method')


class Son(YellowPeopleFather, WhitePersonMother):
    def eat(self):
        print('this is son method')
test=Son('liyuanchao',18)
test.eat()

很容易知道运行结果如下：

• 但是如果此时我们在Son类有eat方法时，但想调用YellowPeopleFather类的方法怎么办勒，根据 MRO 这个顺序：Son->YellowPeopleFather–>WhitePersonMother–>Person–>object。super 的下一个类就是YellowPeopleFather类
  我们只需要对Son类做个小小的改动

class Son(YellowPeopleFather, WhitePersonMother):
    def eat(self):
        super(Son,self).eat()

运行结果如下：

• 当我们想调用WhitePersonMother类中的方法怎么做呢，其实也很简单：

class Son(YellowPeopleFather, WhitePersonMother):
    def eat(self):
        super(YellowPeopleFather,self).eat()

运行结果如下：

• 要用Person中的eat时，同理可得：

class Son(YellowPeopleFather, WhitePersonMother):
    def eat(self):
        super(WhitePersonMother,self).eat()

运行结果如下：

补充一个例子：

class A(object):
    def __init__(self, params):
        self.alive = params['alive']
        self.ok = params['ok']
        self.test = 'test{}'.format(self.alive)

    def a_alive(self):
        print self.alive


class B(object):
    def __init__(self, params):
        self.params = params

    def test_params(self):
        print self.params


class C(A, B):
    def __init__(self, params):
        super(C, self).__init__(params)
        super(A, self).__init__(params)
        self.name = params['name']

    def your_name(self):
        print self.name
        print self.test
        self.test_params()


test = C({'name': 'tom', 'ok': 'okok', 'alive': 'this is alive'})
test.your_name()
test.a_alive()