As long as I'm gravedigging old conversations...! Remember this one, also from January of this year? Here's a link to the thread in the c.l.p-d Mailman archive. The first message in the thread is a good overview of the problem:
Here's kind of where we left it:
On 1/12/21 7:48 PM, Guido van Rossum wrote:
On Tue, Jan 12, 2021 at 6:35 PM Larry Hastings <firstname.lastname@example.org mailto:email@example.com> wrote:
On 1/12/21 5:28 PM, Brett Cannon wrote:
The other thing to keep in mind is we are talking about every module, class, and function getting 64 bytes ... which I bet isn't that much.
Actually it's only every module and class. Functions don't have this problem because they've always stored __annotations__ internally--meaning, peeking in their __dict__ doesn't work, and they don't support inheritance anyway. So the number is even smaller than that. If we can just make __annotations__ default to an empty dict on classes and modules, and not worry about the memory consumption, that goes a long way to cleaning up the semantics.
I would like that very much. And the exception for functions is especially helpful.
First of all, I've proposed a function that should also help a lot:
The function will be called inspect.get_annotations(o). It's like typing.get_type_hints(o) except less opinionated. This function would become the best practice for everybody who wants annotations**, like so:
import inspect if hasattr(inspect, "get_annotations"): how_i_get_annotations = inspect.get_annotations else: # do whatever it was I did in Python 3.9 and before...
** Everybody who specifically wants /type hints/ should instead call typing.get_type_hints(), and good news!, /that/ function has existed for several versions now. So they probably already /do/ call it.
I'd still like to add a default empty __annotations__ dict to all classes and modules for Python 3.10, for everybody who doesn't switch to using this as-yet-unwritten inspect.get_annotations() function. The other changes I propose in that thread (e.g. deleting __annotations__ always throws TypeError) would be nice, but honestly they aren't high priority. They can wait until after Python 3.10. Just these these two things (inspect.get_annotations() and always populating __annotations__ for classes and modules) would go a long way to cleaning up how people examine annotations.
Long-term, hopefully we can fold the desirable behaviors of inspect.get_annotations() into the language itself, at which point we could probably deprecate the function. That wouldn't be until a long time from now of course.
Does this need a lot of discussion, or can I just go ahead with the bpo and PR and such? I mean, I'd JFDI, as Barry always encourages, but given how much debate we've had over annotations in the last two weeks, I figured I should first bring it up here.
p.s. I completely forgot about this until just now--sorry. At least I remembered before Python 3.10b1!