__contains__ classmethod?

[Random832]

On Mon, Dec 18, 2017, at 16:25, Tim Chase wrote:
> My understanding was that "in" makes use of an available __contains__
> but something seems to preventing Python from finding that.
> 
> What's going on here?

Most __ methods have to be an actual method on the class object, which
means you have to use a metaclass.

"one" in X() works, but to get "one" in X to work, you need:

class M(type):
   def __contains__(cls, v):
     return v in cls._ALL

class X(object, metaclass=M):
   ONE = "one"
   TWO = "two"
   _ALL = frozenset(v for k,v in locals().items() if k.isupper())

If you want *both* "one" in X and "one" in X() to work, I think you
pretty much have to define it in both places.