I just got the reply below sent directly to my personal account, and I'm confused about what's going on. If it's just a one off I'll chalk it up to random internet weirdness, but if other folks are getting these too it might be something the list admins should look into? Or... something? ---------- Forwarded message --------- From: Hoi lam Poon <gillcovid19@gmail.com> Date: Fri, Apr 23, 2021, 02:01 Subject: Re: [Python-Dev] Re: PEP 654: Exception Groups and except* [REPOST] To: Nathaniel Smith <njs@pobox.com> Stop pretending, I can definitely get the key control file, your working group, all past actions and instructions cannot be cleared in front of me at all. You have been playing around for a few days, and I won’t stop you. Your face? I won’t, you know, you can’t drive me away, and that file is all, after I get it, you will be convicted even if you disband, I swear 在 2021年4月23日 週五 16:23，Nathaniel Smith <njs@pobox.com> 寫道：
On Wed, Apr 21, 2021 at 4:50 PM Guido van Rossum <guido@python.org> wrote:
On Wed, Apr 21, 2021 at 3:26 PM Nathaniel Smith <njs@pobox.com> wrote:
Sure. This was in my list of reasons why the backwards compatibility tradeoffs are forcing us into awkward compromises. I only elaborated on it b/c in your last email you said you didn't understand why this was a problem :-). And except* is definitely useful. But I think there are options for 'except' that haven't been considered fully.
Do you have any suggestions, or are you just telling us to think harder? Because we've already thought as hard as we could and within all the constraints (backwards compatibility and otherwise) we just couldn't think of a better one.
The main possibility that I don't think we've examined fully is to make 'except' blocks fire multiple times when there are multiple exceptions. We ruled it out early b/c it's incompatible with nested EGs, but if flat EGs are better anyway, then the balance shifts around and it might land somewhere different. it's a tricky discussion though, b/c both the current proposal and the alternative have very complex implications and downsides. So we probably shouldn't get too distracted by that until after the flat vs nested discussion has settled down more.
I'm not trying to filibuster here -- I really want some form of EGs to land. I think python has the potential to be the most elegant and accessible language around for writing concurrent programs, and EGs are a key part of that. I don't want to fight about anything; I just want to work together to make sure we have a full picture of our options, so we can be confident we're making the best choice.
The real cost here is that we would need a new "TracebackGroup" concept, since the internal data structures and APIs keep the traceback chain and the exception object separated until the exception is caught. In our early design stages we actually explored this and the complexity of the data structures was painful. We eventually realized that we didn't need this concept at all, and the result is much clearer, despite what you seem to think.
I'm not talking about TracebackGroups (at least, I think I'm not?). I think it can be done with exactly our current data structures, nothing new.
- When an EG is raised, build the traceback for just that EG while it's unwinding. This means if any C code peeks at exc_info while it's in flight, it'll only see the current branch of the traceback tree, but that seems fine. - When the exception is caught and we go to write back the traceback to its __traceback__ attribute, instead "peek through" the EG and append the built-up traceback entries onto each of the constituent exceptions.
You could get cleverer for efficiency, but that basic concept seems pretty simple and viable to me. What am I missing?
-n
-- Nathaniel J. Smith -- https://vorpus.org _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/VOBOWZGW... Code of Conduct: http://python.org/psf/codeofconduct/