On Thu, Aug 29, 2019 at 3:55 PM Chris Angelico <ros...@gmail.com> wrote:
> On Fri, Aug 30, 2019 at 8:43 AM Guido van Rossum <gu...@python.org> wrote: > > > > 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.) > > No, I mean that at run-time, int|str might return a very simple object > in 3.9, rather than everything that you'd need to grab from importing > typing. Wondering if doing so would close off the possibility of, in > 3.12 or something, making it a more directly usable "type union" that > has other value. > I think typing shuld just re-export the builtin Union and deal with it. -- --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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