On 26 November 2014 at 04:04, Guido van Rossum <gu...@python.org> wrote: > On Tue, Nov 25, 2014 at 9:49 AM, Chris Angelico <ros...@gmail.com> wrote: >> >> On Wed, Nov 26, 2014 at 4:45 AM, Isaac Schwabacher >> <ischwabac...@wisc.edu> wrote: >> > Yield can also raise StopIteration, if it's thrown in. The current >> > interaction of generator.throw(StopIteration) with yield from can't be >> > emulated under the PEP's behavior, though it's not clear that that's a >> > problem. >> > >> >> Hrm. I have *absolutely* no idea when you would use that, and how >> you'd go about reworking it to fit this proposal. Do you have any >> example code (production or synthetic) which throws StopIteration into >> a generator? > > > Sounds like a good one for the obfuscated Python contest. :-) > > Unless the generator has a try/except surrounding the yield point into which > the exception is thrown, it will bubble right out, and PEP 479 will turn > this into a RuntimeError. I'll clarify this in the PEP (even though it > logically follows from the proposal) -- I don't think there's anything to > worry about.
This is actually the edge case that needs to be handled in contextlib - a StopIteration raised by the with statement body gets thrown into the generator implementing the context manager. My current porting recommendation is to catch the RuntimeError & look at __cause__ to see if it's the StopIteration instance that was thrown in, but an alternative option would be to just call gen.close() in that case, rather than gen.throw(exc). Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
