Are you saying that hasattr returning False was hiding a bug or is a bug? The former could be annoying to track down, though hasattr(X, 'y') == True. For the latter, having hasattr return False if an AttributeError is raised would allow the property decorator to retain identical functionality if it is used to replace a (sometimes) existing attribute. On Sun, Dec 25, 2016 at 1:24 PM, Zahari Dim <zaharid@gmail.com> wrote:
Hi,
The other day I came across a particularly ugly bug. A simplified case goes like:
class X: @property def y(self): return self.nonexisting
hasattr(X(),'y')
This returns False because hasattr calls the property which in turn raises an AttributeError which is used to determine that the property doesn't exist, even if it does. This is arguably unexpected and surprising and can be very difficult to understand if it happens within a large codebase. Given the precedent with generator_stop, which solves a similar problem for StopIteration, I was wondering if it would be possible to have the __get__ method convert the AttributeErrors raised inside it to RuntimeErrors.
The situation with this is a little more complicated because there could be a (possibly strange) where one might want to raise an AttributeError inside __get__. But maybe the specification can be changed so either `raise ForceAttributeError()` or `return NotImplemented` achieves the same effect.
Merry Christmas! Zahari. _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/