Python:无法使用 super() 调用父类析构函数

Question

我无法从子类的析构函数中调用父类的析构函数。 请检查以下代码:

class BaseClass(object):
    def __del__(self):
        print 'BaseClass->Destructor'

class DerivativeClass(BaseClass):
    def __del__(self):
        print 'DerivativeClass->Destructor'
        #Invoke destructor of the base class, it works 
        BaseClass.__del__(self)           
        #Doesn't work
        #super(DerivativeClass, self).__del__() 

instance = DerivativeClass()

当我在 DerivativeClass.__del__() 中使用 super(DerivativeClass, self).__del__() 时，出现以下错误:

Exception TypeError: 'must be type, not None' in <bound method 
DerivativeClass.__del__ of <__main__.DerivativeClass object at 0xb73a682c>> ignored

问题:

为什么我不能在子类的析构函数中使用 super 而它在子类的构造函数中完全没问题？

Answer 1

这似乎只发生在运行时退出(因为 DerivativeClass 是 None)。

这很好用:

class BaseClass(object):
    def __del__(self):
        print 'BaseClass->Destructor'

class DerivativeClass(BaseClass):
    def __del__(self):
        print 'DerivativeClass->Destructor'
        super(DerivativeClass, self).__del__() 

instance = DerivativeClass()
del instance

这也很好用:

class BaseClass(object):
    def __del__(self):
        print 'BaseClass->Destructor'

class DerivativeClass(BaseClass):
    def __del__(self):
        print 'DerivativeClass->Destructor'
        super(type(self), self).__del__() 

instance = DerivativeClass()

还有这个:

class BaseClass(object):
    def __del__(self):
        print 'BaseClass->Destructor'

class DerivativeClass(BaseClass):
    def __del__(self):
        print 'DerivativeClass->Destructor'
        super(DerivativeClass, self).__del__() 

def someScope ():
    instance = DerivativeClass()

someScope ()

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在片段 1 和片段 3 中，我确保实例在类之前结束。在片段 2 中，我以一种非常丑陋的方式绕过了整个问题。