El jue, 21 oct 2021 a las 10:31, Carl Meyer (<c...@oddbird.net>) escribió:
> On Thu, Oct 21, 2021 at 10:44 AM Damian Shaw > <damian.peter.s...@gmail.com> wrote: > > Sorry for the naive question but why doesn't "TYPE_CHECKING" work under > PEP 649? > > > > I think I've seen others mention this but as the code object isn't > executed until inspected then if you are just using annotations for type > hints it should work fine? > > > > Is the use case wanting to use annotations for type hints and real time > inspection but you also don't want to import the objects at run time? > > Yes, you're right. And I don't think PEP 649 and PEP 563 are really > all that different in this regard: if you have an annotation using a > non-imported name, you'll be fine as long as you don't introspect it > at runtime. If you do, you'll get a NameError. And with either PEP you > can work around this if you need to by ensuring you do the imports > first if you're going to need the runtime introspection of the > annotations. > > The difference is that PEP 563 makes it easy to introspect the > annotation _as a string_ without triggering NameError, and PEP 649 > takes that away, but I haven't seen anyone describe a really > compelling use case for that. > > I would want this for my type checker, pyanalyze. I'd want to get the raw annotation and turn it into a type. For example, if the annotation is `List[SomeType]` and `SomeType` is imported in `if TYPE_CHECKING`, I'd at least still be able to extract `List[Any]` instead of bailing out completely. With some extra analysis work on the module I could even get the real type out of the `if TYPE_CHECKING` block.
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