On Thu, Jul 29, 2021 at 4:52 PM Nick Coghlan <ncogh...@gmail.com> wrote:
>
> On Fri, 30 Jul 2021, 6:05 am Mark Shannon, <m...@hotpy.org> wrote:
>>
>> Hi Nick,
>>
>> Our discussion on PEP 558 got me thinking
>> "What is the simplest thing that would work?".
>>
>> This is what I came up (in the form of a draft PEP):
>> https://github.com/markshannon/peps/blob/pep-locals/pep-06xx.rst
>>
>> It doesn't have O(1) len(f_locals), and it does break
>> `PyEval_GetLocals()` but I think the that is a small price to pay for
>> simplicity and consistency.
>
>
> I don't think it is OK to break PyEval_GetLocals() when we really don't need
> to,
> and the proposal also discards all the feedback that I received on earlier
> iterations of PEP 558. (I particularly recommend reading Nathaniel's analysis
> of why returning the proxy from locals() would be more likely to cause bugs
> in existing code than it would be to eliminate any).
Heh, I was actually just re-reading PEP 558 and going to ask you to
include more details to justify the complexity, as compared to
something like Mark's latest proposal here -- I'd totally forgotten I
wrote that old post :-). So that was a timely reminder!
Looking at the references in the PEP, is this the writeup you're talking about?
https://mail.python.org/pipermail/python-dev/2019-May/157738.html
The conclusion there is:
> I'm leaning towards saying that on net, [snapshot] beats [PEP-minus-tracing]:
> it's dramatically simpler, and the backwards incompatibilities that we've
> found so far seem pretty minor, on par
with what we do in every point release. (In fact, in 3/4 of the cases
I looked at, [snapshot] is actually what users seemed to trying to use
in the first place.)
>
> For [proxy] versus [snapshot], a lot depends on what we think of changing the
> semantics of exec(). [proxy] is definitely more consistent and elegant, and
> if we could go back in time I think it's
what we'd have done from the start. Its compatibility is maybe a bit
worse than [snapshot] on non-exec() cases, but this seems pretty minor
overall (it often doesn't matter, and if it does just write
dict(locals()) instead of locals(), like you would in non-function
scope). But the change in exec() semantics is an actual language
change, even though it may not affect much real code, so that's what
stands out for me.
I *think* (please correct me if I'm wrong) that what that calls
[PEP-minus-tracing] is now corresponds to the current PEP draft, and
[proxy] corresponds to Mark's draft at the beginning of this thread?
-n
--
Nathaniel J. Smith -- https://vorpus.org
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