Well, it's not an object of type 'type' like the list or dict mentioned
by the OP, for which len() give a
TypeError: object of type 'type' has no len()
Any derived class of Enum will also return True for
isinstance(..., type). Should the derived classes then neither have a
meaningful result for len()? Enum and derived classes hold a container
with a fixed set of values. It makes perfectly sense to ask for the
number of possible values, even when there are none.
Op 3/04/2023 om 08:53 schreef Chris Angelico:
On Mon, 3 Apr 2023 at 15:54, Benedict Verhegghe <[email protected]> wrote:
Enum is not a type, like the OP suggested:
Well, it is:
isinstance(Enum, type)
True
but it has a metaclass, meaning that the type of Enum is a subclass of type.
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
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