类的继承和实现原理

Posted 2021-01-06 huizaia

1.类的继承实例

class Hero:
    aa = ‘11‘

    def __init__(self, name, life, damage):
        self.name = name
        self.life = life
        self.damage = damage

    def attack(self, enemy):
        enemy.life -= self.damage


class Hero1(Hero):
    pass


st1 = Hero1(‘gaohui‘, ‘100‘, 50)
print(st1.__dict__)
print(Hero1.__bases__)
print(st1.aa)



输出结果为：
{‘name‘: ‘gaohui‘, ‘life‘: ‘100‘, ‘damage‘: 50}
(<class ‘__main__.Hero‘>,)
11

 

类的继承中一个易错点

当父类和子类中有相同的方法时，谁的对象调就是谁的方法

class Foo:

    def f1(self):
        print(‘from Foo.f1‘)

    def f2(self):
        print(‘from Foo.f2‘)
        self.f1()  # 哪个对象调就是对象的f1 ，所以这个方法就是b的f1


class Bar(Foo):
    def f1(self):
        print(‘from Bar.f2‘)


b = Bar()
b.f2()


输出结果：

from Foo.f2
from Bar.f2

 

 

继承的实现原理

当类是新式类时，在多继承时，查找的属性不存在时，会按广度优先（即不会先找到父类）去找。

class A(object):
    def test(self):
        print(‘from A‘)


class B(A):
    def test(self):
        print(‘from B‘)


class C(A):
    def test(self):
        print(‘from C‘)


class D(B):
    def test(self):
        print(‘from D‘)


class E(C):
    def test(self):
        print(‘from E‘)


class F(D, E):
    pass


print(F.mro())  # 得出广度优先选择的顺序


结果
[<class ‘__main__.F‘>, <class ‘__main__.D‘>, <class ‘__main__.B‘>, <class ‘__main__.E‘>, <class ‘__main__.C‘>, <class ‘__main__.A‘>, <class ‘object‘>]