Of course, languages evolve. Annotations were introduced just for function arguments, now we use them almost everywhere. Generators were simply loop managers, now they've blown up to complete asynchronous programming beasts. Ellipsis was introduced for easier slicing of n-dimensional objects, now we have it all over the language - precisely because it's so versatile. NotImplemented, I _think_ (but I'm really no expert), is not.

As you say, we currently have only one usage of NotImplemented outside its intended purpose. Maybe we should wait to see whether it becomes at least a little bit more popular, before thinking about blessing it.

About Raymond's post: well, there can be orthogonal reasons why something isn't a good idea. That doesn't mean it _is_ a good idea. :-]