[Python-Dev] Adding Type[C] to PEP 484 (original) (raw)

Peter Ludemann pludemann at google.com
Sat May 14 14:47:15 EDT 2016

I think that Type[C,D] would mean Union[Type[C], Type[D]], but I'm not sure ... I should probably talk to a typing expert about this. (Sorry for thinking out loud; but if we decide that Type[C,D] doesn't make sense, we need to prohibit it)

I suppose I'm asking: do we allow new_user(Type[BasicUser, ProUser])?

Here's a trivial example that off the top of my head makes sense:

BasicOrProUser = TypeVar('BasicOrProUser', BasicUser, ProUser) def new_user(name: str, user_factory: Type[BasicOrProuser]) -> BasicOrProUser: return user_factory(name)

Or must the Type[...] item have been defined with a TypeVar(..., bound=...), in which case multiple types aren't allowed with Type[...]?

On 14 May 2016 at 11:30, Guido van Rossum <gvanrossum at gmail.com> wrote:

What would Type[C, D] mean?

--Guido (mobile) On May 14, 2016 11:21 AM, "Peter Ludemann via Python-Dev" <_ _python-dev at python.org> wrote:

Is Type[C,D] allowed? Or should multiple types be restricted to TypeVar?

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