Terry J. Reedy <tjreedy@udel.edu> added the comment: https://docs.python.org/3/reference/datamodel.html#customizing-instance-and-... says "Note that these methods are looked up on the type (metaclass) of a class. They cannot be defined as class methods in the actual class. This is consistent with the lookup of special methods that are called on instances, only in this case the instance is itself a class." IE, your first example is documented as wrong. Your second example, which works, follows the example in https://docs.python.org/3/reference/datamodel.html#customizing-instance-and-... ---------- nosy: +terry.reedy resolution: -> not a bug stage: -> resolved status: open -> closed versions: +Python 3.8 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue33417> _______________________________________