I love the proposal for dicts, but I agree that this discourages duck typing. Could the curly braces notation represent Mapping, not dict specifically?

+1 to shortening tuples but not other sequences.

Finn Mason

On Thu, Oct 14, 2021, 6:46 AM Paul Moore <p.f.moore@gmail.com> wrote:
On Thu, 14 Oct 2021 at 13:04, Ricky Teachey <ricky@teachey.org> wrote:
> I think all of this additional syntax is just a mistake.
> The reason is it will encourage people to not properly annotate their input types for duck typing. Some of these shortcuts might be nice for output types. But the more general trying.Mapping, typing.Sequence and friends should be preferred for input types. If terse shortcuts are available for the concrete data structure types, but not for the generic types, a lot of people are going to feel nudged to type hint their python improperly.

+1. I'm not sure how much of my reservations about this whole
discussion are ultimately reservations about typing in general, but I
feel that the more we make it easier to express "exact" types, the
more we encourage people to constrain their APIs to take precise types
rather than to work with duck types. (I saw an example recently where
even Mapping was over-specified, all that was needed was __getitem__,
not even __len__ or __iter__).

I know protocols allow duck typing in a static type checking context -
maybe the energy focused on "making basic types easier to write"
should be focused on making protocols easier to write, instead.

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