Python-28 类和对象：继承

继承

语法：class DerivedClassName(BaseClassName):  在括号里加上父类的名字。

被继承的类叫基类、父类或超类。而继承者称为子类，子类可以继承父类的所有属性和方法。

>>> class Parent:
def hello(self):
print('正在调用父类....')


>>> class Child(Parent):
pass

>>> p = Parent()
>>> p.hello()
正在调用父类....
>>> c = Child()
>>> c.hello()
正在调用父类....
>>> 

如果子类中定义与父类同名的方法或属性，则会自动覆盖父类对应的方法或属性。

>>> class Child(Parent):
def hello(self):
print('正在调用子类方法')


>>> c = Child()
>>> c.hello()
正在调用子类方法
>>> p = Parent()
>>> p.hello()
正在调用父类....
>>> 

—调用未绑定的父类方法

import random as r

class Fish:
    def __init__(self):
        self.x = r.randint(0,10)
        self.y = r.randint(0,10)

    def move(self):
        self.x -=1
        print('我的位置是：',self.x,self.y)

class Goldfish(Fish):
    pass

class Carp(Fish):
    pass

class Salmon(Fish):
    pass

class Shark(Fish):
    def __init__(self):
        Fish.__init__(self)
        self.hungry = True

    def eat(self):
        if self.hungry:
            print('eating......')
            self.hungry = False
        else:
            print('吃太多了....')

—使用super函数

直接使用super()，也不用self参数

import random as r

class Fish:
    def __init__(self):
        self.x = r.randint(0,10)
        self.y = r.randint(0,10)

    def move(self):
        self.x -=1
        print('我的位置是：',self.x,self.y)

class Goldfish(Fish):
    pass

class Carp(Fish):
    pass

class Salmon(Fish):
    pass

class Shark(Fish):
    def __init__(self):
        super().__init__()
        self.hungry = True

    def eat(self):
        if self.hungry:
            print('eating......')
            self.hungry = False
        else:
            print('吃太多了....')

多重继承

class DerivedClassName(Base1, Base2, Base3):

>>> class Base1:
def fool1(self):
print('Base1......')


>>> class Base2:
def fool2(self):
print('Base2......')


>>> class C(Base1 ,Base2):
pass

>>> c = C()
>>> c.fool1()
Base1......
>>> c.fool2()
Base2......
>>> 

多重继承，很容易导致代码混乱。