[Python-ideas] Re: len(Enum) should raise TypeError

On Mon, 3 Apr 2023 at 15:54, Benedict Verhegghe <bverheg@gmail.com> wrote:

Enum is not a type, like the OP suggested:

Well, it is:

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isinstance(Enum, type) True

but it has a metaclass, meaning that the type of Enum is a subclass of type.

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type(Enum) <class 'enum.EnumType'> type(Enum).__bases__ (<class 'type'>,)

I mean, we wouldn't be subclassing it if it weren't a type. The __len__ method is implemented on the metaclass to allow all Enum subclasses to have lengths (ditto __iter__ to make them iterable), and as a consequence of that, Enum itself has all the attributes that it wants to give to its subclasses. ChrisA