On Sun, Nov 6, 2016 at 8:53 AM, Nick Coghlan <ncogh...@gmail.com> wrote:
> On 6 November 2016 at 16:07, Ram Rachum <r...@rachum.com> wrote: > > Heh, I just played with this, and found a workaround. If I do something > like > > this after creating the generator: > > > > sys.g = g > > > > Then it wouldn't get closed when Python finishes, and the cleanup won't > > happen, which is what I want. > > The interpreter goes to significant lengths to make sure that finally > clauses get executed prior to or during interpreter shutdown, and any > means you find by which they don't get executed is considered a bug > (not always a fixable bug, but a bug nonetheless). If you rely on > those bugs and limitations to get your program to perform the way you > want it to you're going to run into problems later when upgrading to > new CPython versions, or trying out different interpreter > implementations. > I understand, and I agree with the reasoning. Still, I think I'll take my chances. There's still something seriously odd going in relation to your > overall resource management architecture if "cleanup, maybe, unless I > decide to tell you not to" is a behaviour you regularly need. Cleanup > functions in a garbage collected environment should be idempotent, so > it doesn't matter if you redundantly call them again later. > Well, you think it's weird that I want a `finally` clause to not be called in some circumstances. Do you think it's equally weird to want an `__exit__` method that is not called in some circumstances? > > However, if you *do* need that pattern regularly, then the pattern > itself can be encapsulated in a context manager: > > class callback_unless_exit: > def __init__(self, callback): > self.callback = callback > def __enter__(self): > return self > def __exit__(self, exc_type, exc_value, exc_tb): > if issubclass(exc_type, GeneratorExit): > return > self.callback() > > and then do: > > with callback_unless_exit(cleanup): > yield > > in the context managers where you want that behaviour. > > Thanks for the workaround but I feel it's even less elegant than my original workaround.
_______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
