多重继承和超级继承

Question

为什么这只在我从Second中的__init__中删除config时才起作用

class First(object):
    def __init__(self, config):
        super().__init__(config)
        print("first", config)

class Second(object):
    def __init__(self, config): # <-- works only if I remove config
        super().__init__(config)
        print("second", config)

class Third(First, Second):
    def __init__(self, config):
        super().__init__(config)
        print("third", config)
        
Third({"name": "alex"})

=> second {'name': 'alex'}
=> first {'name': 'alex'}
=> third {'name': 'alex'}

Answer 1

错误消息准确地告诉您出了什么问题：

TypeError: object.__init__() takes exactly one argument (the instance to initialize)

Second的父类是object，您用一个额外的参数调用它的__init__。

super()只给了你第一个父类，这使得它在你进行多重继承时通常没有帮助(而且经常是纯粹的混乱)。如果修复代码以消除调用object.__init__(config)时出现的错误，则会得到：

class First:  # note that in modern Python you don't need to give object as the parent
    def __init__(self, config):
        print("first", config)

class Second:
    def __init__(self, config):
        print("second", config)

class Third(First, Second):
    def __init__(self, config):
        super().__init__(config)
        print("third", config)
        
Third({"name": "alex"})

first {'name': 'alex'}
third {'name': 'alex'}

因为您的super().__init__调用只调用First。相反，您可能希望显式调用每个父类的构造函数：

class Third(First, Second):
    def __init__(self, config):
        First.__init__(self, config)
        Second.__init__(self, config)
        print("third", config)

first {'name': 'alex'}
second {'name': 'alex'}
third {'name': 'alex'}