On Thu, Aug 29, 2019 at 3:33 PM Chris Angelico <ros...@gmail.com> wrote:
> On Fri, Aug 30, 2019 at 8:28 AM Guido van Rossum <gu...@python.org> wrote: > > Open question: at runtime, what should `int | str` return? I don't want > this to have to import the typing module. Maybe we could make a very simple > `Union` builtin. This can then also be used by `~int` (which is equivalent > to `int | None`). > > > > Would it be okay to have a very simple Union builtin now, and it just > always returns exactly that, and then in the future it might > potentially actually return Union[int, str] ? > > I'm not pushing for it *now*, but it would be extremely handy in the > future to be able to say isinstance(3, int|str) and have it be > meaningful. > Are you suggesting we introduce the "very simple Union builtin" earlier than the "int | str" notation/implementation? Why? 3.8 is closed for features, so it would be 3.9 at the earliest -- plenty of time to implement this right (including `isinstance(x, int|str)`). I do think we should probably review PEP 585 before doing anything about unions specifically -- likely there are bigger fish to fry. (And PEP 585 has not received much discussion.) -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him/his **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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