【问题与解决】python 子类中使用json.dumps出现TypeError: Object of type super is not JSON serializable错误的解决办法

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问题描述

• 在使用python json.dumps()方法输出dict格式内容：

class MyClass(dict):
	def __init__(self):
		...


json.dumps(super(MyClass, self), ensure_ascii=False)

• 运行时出现错误：TypeError: Object of type super is not JSON serializable

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问题分析

• python中super并非关键字，而是一个builtin的一个class，虽然dict本身时可以被json.dumps的，但super类dumps方法并不认，所以导致了这个问题的发生。
• 查看super 源码：

class super(object):
    """
    super() -> same as super(__class__, )
    super(type) -> unbound super object
    super(type, obj) -> bound super object; requires isinstance(obj, type)
    super(type, type2) -> bound super object; requires issubclass(type2, type)
    Typical use to call a cooperative superclass method:
    class C(B):
        def meth(self, arg):
            super().meth(arg)
    This works for class methods too:
    class C(B):
        @classmethod
        def cmeth(cls, arg):
            super().cmeth(arg)
    """
    def __getattribute__(self, *args, **kwargs): # real signature unknown
        """ Return getattr(self, name). """
        pass

    def __get__(self, *args, **kwargs): # real signature unknown
        """ Return an attribute of instance, which is of type owner. """
        pass

    def __init__(self, type1=None, type2=None): # known special case of super.__init__
        """
        super() -> same as super(__class__, )
        super(type) -> unbound super object
        super(type, obj) -> bound super object; requires isinstance(obj, type)
        super(type, type2) -> bound super object; requires issubclass(type2, type)
        Typical use to call a cooperative superclass method:
        class C(B):
            def meth(self, arg):
                super().meth(arg)
        This works for class methods too:
        class C(B):
            @classmethod
            def cmeth(cls, arg):
                super().cmeth(arg)
        
        # (copied from class doc)
        """
        pass

    @staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

    def __repr__(self, *args, **kwargs): # real signature unknown
        """ Return repr(self). """
        pass

    __self_class__ = property(lambda self: type(object))
    """the type of the instance invoking super(); may be None

    :type: type
    """

    __self__ = property(lambda self: type(object))
    """the instance invoking super(); may be None

    :type: type
    """

    __thisclass__ = property(lambda self: type(object))
    """the class invoking super()

    :type: type
    """

• 可以看到，__self__变量为实际super所指向的class实例，这才是dumps方法真正想要的内容。

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解决方法

• 将代码修改如下即可成功运行：

json.dumps(super(MyClass.__self__, self), ensure_ascii=False)

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