On Fri, Nov 26, 2021 at 1:47 PM Guido van Rossum <gu...@python.org> wrote > It's easy enough to do something at runtime with `def f(a: list[int]) -> int`. It's not so simple to handle `def f(a: Sequence[T]) -> T` or `def f(cb: (T) -> tuple[str, T], Sequence[T]) -> Mapping[str, T]`. Presumably frameworks like pydantic just don't support such things and tell the user not to do that.
I don’t know about Pydantic, but that’s exactly my use case: the type needs to be an actual intstantiatable type. So list and tuple is fine, and Sequence[t] won’t work. But it’s fine that this use case is restricted. In fact, other than the basic core types, you need to use specialized types with this system anyway. -CHB -- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
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