面向对象特性—继承与接口（三十）

import abc

class AllFile(metaclass=abc.ABCMeta):
    @abc.abstractmethod
    def read(self):
        pass
    # 父类定义抽象的方法，子类必须实现
    @abc.abstractmethod
    def write(self):
        pass

class Txt(AllFile):
    def read(self):
        print("txt read")
    def write(self):
        print("txt write")

class Mem(AllFile):
    def read(self):
        print("mem read")
    def write(self):
        print("mem write")

m = Mem()
m.read()
m.write()

继承顺序：

Java ，C#只能继承一个类，Python可以继承多个类

class A:
    def test(self):
        print("this is A")

class B(A):
    # def test(self):
    #     print("this is B")
    pass

class D(B):
    # def test(self):
    #     print("this is D")
    pass

class C(A):
    # def test(self):
    #     print("this is C")
    pass

class E(C):
    # def test(self):
    #     print("this is E")
    pass

class F(D,E):
    # def test(self):
    #     print("this is F")
    pass

print(F.__mro__)
'''
F.__mro__ 揭秘了F的继承顺序
(<class '__main__.F'>, <class '__main__.D'>, <class '__main__.B'>, 
<class '__main__.E'>, <class '__main__.C'>, <class '__main__.A'>, <class 'object'>)
'''
f = F()
f.test() # F-->D-->B-->E-->C-->A

Python会计算一个方法解析顺序（MRO) 列表，这个列表就是一个简单的所有基类的线性顺序表

注意：Python2 与Python3 中的继承顺序是不一样的

子类中调用父类的方法

class Vehicle:
    Country = "China"
    def __init__(self,name,speed,load,power):
        self.Name = name
        self.Speed = speed
        self.Load = load
        self.Power = power

    def run(self):
        print("running...")

class Subway(Vehicle):
    def __init__(self,name,speed,load,power,line):
        Vehicle.__init__(self,name,speed,load,power)
        self.Line = line

    def show_info(self):
        print("%s %d号线" %(self.Name,self.Line))

    def run(self):
        Vehicle.run(self)
        print("%s %d号线，以%s的速度在运行" %(self.Name,self.Line,self.Speed))

line3 = Subway("深圳地铁","100km/s",10000,"电",3)
line3.show_info()
line3.run()
'''
深圳地铁 3号线
running...
深圳地铁 3号线，以100km/s的速度在运行
'''

super调用父类的方法

class Vehicle:
    Country = "China"
    def __init__(self,name,speed,load,power):
        self.Name = name
        self.Speed = speed
        self.Load = load
        self.Power = power

    def run(self):
        print("running...")

class Subway(Vehicle):
    def __init__(self,name,speed,load,power,line):
        # Vehicle.__init__(self,name,speed,load,power)
        super().__init__(name,speed,load,power)
        self.Line = line

    def show_info(self):
        print("%s %d号线" %(self.Name,self.Line))

    def run(self):
        # Vehicle.run(self)
        super().run()
        print("%s %d号线，以%s的速度在运行" %(self.Name,self.Line,self.Speed))

line3 = Subway("深圳地铁","100km/s",10000,"电",3)
line3.show_info()
line3.run()
'''
深圳地铁 3号线
running...
深圳地铁 3号线，以100km/s的速度在运行
'''