015: class and objects > 多重继承

1. 简单多重继承：

多重继承一个比较麻烦的问题就是父类的初始化的问题，下面这个例子算是一般比较常见的方式。但是这种方式存在着一个问题，那就是object的初始化函数将运行两次，一般情况下这不会产生什么问题，但是有时候可能会引起设计上的致命缺陷。

class Mother(object):
    def __init__(self, first_name):
        self.first_name = first_name

class Father(object):
    def __init__(self, last_name):
        self.last_name = last_name

class Child(Mother, Father):
    def __init__(self, first_name, last_name):
        Mother.__init__(self, first_name)
        Father.__init__(self, last_name)

Tom = Child('Tom', 'Jim')    

print(Tom.first_name, Tom.last_name)

 下面的例子体现了父类初始化两次的例子，一般情况下，这并不是太常见。

class BaseClass(object):
    def __init__(self, age):
        self.age = age
        print("BaseClass' __init__ is invoked.")

class Mother(BaseClass):
    def __init__(self, first_name, age):
        BaseClass.__init__(self, age)
        self.first_name = first_name

class Father(BaseClass):
    def __init__(self, last_name, age):
        BaseClass.__init__(self, age)
        self.last_name = last_name

class Child(Mother, Father):
    def __init__(self, first_name, last_name, age):
        Mother.__init__(self, first_name, age)
        Father.__init__(self, last_name, age)

Tom = Child('Tom', 'Yao', 12)    

print(Tom.first_name, Tom.last_name)

 

2. 使用字典参数来实现，爷爷类只被调用一次

class BaseClass(object):
    def __init__(self, age = '', **kwargs):
        self.age = age
        print("BaseClass' __init__ is invoked.")

class Mother(BaseClass):
    def __init__(self, first_name = '', **kwargs):
        super().__init__(**kwargs)
        self.first_name = first_name

class Father(BaseClass):
    def __init__(self, last_name = '', **kwargs):
        super().__init__(**kwargs)
        self.last_name = last_name

class Child(Mother, Father):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

Tom = Child(**{"age":21, "first_name":"Miles", "last_name":"Yao"})    

print(Tom.first_name, Tom.last_name)