On Thu, May 25, 2017 at 7:19 AM, Nick Coghlan <ncoghlan@gmail.com> wrote:
Given the abstract, I'd suggest "Structural Subtyping" as a suitable
title for the PEP.

Maybe even "Structural Subtyping (a.k.a. Duck Typing)"

That said, I think it's fine to use "protocol" throughout the rest of
the PEP as is currently the case - object protocols and network
protocols are clearly different things, it's just the bare word
"Protocols" appearing as a PEP title in the PEP index with no other
context that's potentially confusing.

I'm +1 on the general idea of the PEP, and only have one question
regarding the specifics. Given:

    import typing

    class MyContainer:
        def __len__(self) -> int:
        def close(self) -> None:

Would that be enough for a static typechecker to consider MyContainer
a structural subtype of both typing.Sized and SupportsClose from the
PEP, even though neither is imported explicitly into the module? I'm
assuming the answer is "Yes", but I didn't see it explicitly stated

Yes. Imports don't enter the matter. (Things get tied together at the call sites.) @Ivan: if there isn't an example that makes this clear we should add one.

--Guido van Rossum (python.org/~guido)