对Python中的超级函数和自相混淆

Posted 2021-04-19

这里是代码使我感到困惑。

#python3 code
class SuperClass():
    def __init__(self,a):
        self.a = a

class SubClass(SuperClass):
    def __init__(self,a):
        self.a = a
        super(SubClass,self).__init__(a+1)


if __name__ == '__main__':
    sub = SubClass(1)
    print(sub.a) # result is 2
    # print(super(SubClass,sub).a) # AttributeError: 'super' object has no attribute 'a'

我想在调用super(SubClass,self).__init__(a+1)时，对象sub传递给SuperClass中的self，不是子对象的父对象。

我有2个问题：

1. 我的猜测正确吗？如果正确，为什么要这样设计？如果不是，什么是正确的机械装置？
2. 我如何将值a + 1传递给SuperClass.a，换句话说，使super(SubClass,sub).a=2

谢谢

编辑1

对代码感到抱歉。我将self.a=a和super(SubClass,self).__init__(a+1)两行放错了地方。我已经纠正了上面的代码，它仍然支持我的猜测。

编辑2

#Let me explain my doubt in detail
#Generally We have a class Clazz
class Clazz():
    def f(self,a):
        pass
# and it's instance c
c = Clazz();
# when invoke method f of instance c, instance should be  implicit pass to the method as first parameter.
c.f(1) # formally equivalent to c.f(c,1)

#then back to my case
#In my logic
# super(SubClass,self) is a instance of class super ,when it invokes method __init__
# Similarly super(SubClass,self).__init__(a+1) should be equivalent to super(SubClass,self).__init__(super(SubClass,self),a+1)
class SuperClass():
    def __init__(self,a):   #  self=super(SubClass,sub)
        self.a = a          #  formally equivalent to super(SubClass,sub).a = a

# however it's not like as i thought
# super(SubClass,self).__init__(a+1) formally equivalent to super(SubClass,self).__init__(sub,a+1)
class SuperClass():
    def __init__(self,a):   #  self=sub
        self.a = a          #  formally sub.a = a
# it's contradictory

答案

简短的回答：不可能。

长答案：您的SubClass继承自SuperClass。初始化sub的对象SubClass时，它将进入__init__的SubClass。在那里它告诉它运行__init__的SuperClass，其中sub.a的值设置为2，但是在SubClass中立即将值1写入sub.a。

值sub.a被覆盖。没了该变量仅存在一次，而不是两次。在这种情况下，您的SubClass和SuperClass引用相同的变量sub.a

如果要保留值，则需要定义一个新变量并在其中写入值。

#python3 code class SuperClass(): def __init__(self,var): self.a = var class SubClass(SuperClass): def __init__(self,var): super(SubClass,self).__init__(var+1) self.b = var if __name__ == '__main__': sub = SubClass(1) print(sub.a) print(sub.b)