Your link appears not to work (for me) — can you cite what you believe I have incorrect? This section seems to agree with me, where it explains why normal clas

Your link appears not to work (for me) — can you cite what you believe I have incorrect? This section seems to agree with me, where it explains why normal classes can’t be subclassed to protocols: > Now, C is a subtype of Proto, and Proto is a subtype of Base. But C cannot be a subtype of Base (since the latter is not a protocol). This situation would be really weird. In addition, there is an ambiguity about whether attributes of Base should become protocol members of Proto. https://peps.python.org/pep-0544/#protocols-subclassing-normal-classes https://peps.python.org/pep-0544/#protocols-subclassing-norm... - - - - I’m not sure why you think it’s “obvious” that you can use a third party library to solve the problem — or why that addresses my complaint that the built-in type system doesn’t work for that. If anything, the existence of a third party library hints the standard library doesn’t cover the use case.