Hi Ethan, See Irit's response to my about why ExceptionGroup doesn't subclass Exception -- I think this is still a little bit of an open issue.
Another response (which I also read somewhere in one of Irit's messages) is that a library API shouldn't go from raising subclasses of Exception only to raising ExceptionGroups. That would be a backwards incompatible change to an API. --Guido On Tue, Feb 23, 2021 at 8:52 PM Ethan Furman <et...@stoneleaf.us> wrote: > On 2/23/21 7:56 PM, Guido van Rossum wrote: > > On Tue, Feb 23, 2021 at 7:37 PM Ethan Furman wrote: > > >> It sounds like the long-term goal is to move away from `except` and > >> replace it with `except *` -- is that correct? > > > > I don't think so -- if we expected that to happen the extra '*' in the > > syntax would be a nuisance. The premise of the PEP is rather that > > raising and catching multiple exceptions at once is always going > > to be an esoteric hobby. The most common case by far would be in async > > frameworks, but we don't expect 'async def' to eventually become the > > standard function definition either (nor 'await f()' the standard call > :-). > > > > And even in an async framework, I don't expect that every async function > > would be "upgraded" to raise ExceptionGroup -- only specific APIs like > > gather() or create_connection(). (Even for those, backwards compatibility > > concerns will probably mean that we'll have to introduce *new* APIs that > > can raise ExceptionGroup.) The PEP lists a handful of other use cases, > > none of which seem to suggest to me that this is going to be a common > thing. > > I can see the value in `except *` for concurrent code; my concern is how > it will operate with the standard `try/except` framework. With the new > non-Exception-derived ExceptionGroup class, existing try-excepts that catch > Exception will fail for every ExceptionGroup that leaks through; the fix > for that is a doubly-nested try-except/try-except* -- what do we get for > that code churn? What is the advantage in not deriving from Exception? If > I recall correctly, we have only three exception types that derive directly > from BaseException: Exception, SystemExit, and KeyboardInterrupt -- with > SystemExit and KeyboardInterrupt both being concerned with making sure an > application can quit. > > -- > ~Ethan~ > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@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/445RAHP7XXLQFFGFKCXITPQPGAB55MDY/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
_______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@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/5JEJ2TM7VQIJPPH6SIJNTWX5BOCTS3CH/ Code of Conduct: http://python.org/psf/codeofconduct/
