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:
https://mail.python.org/archives/list/[email protected]/thread/AWKVI3NRCHKPIDPCJYGVLW4HBYTEOQYL/
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 <[email protected]
<mailto:[email protected]>> 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:
https://bugs.python.org/issue43817
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.
Happy two-weeks'-notice,
//arry/
p.s. I completely forgot about this until just now--sorry. At least I
remembered before Python 3.10b1!
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