[Python-3000] exception-swallowing behaviour of hasattr
lists at cheimes.de
Tue Jan 22 08:14:20 CET 2008
Dwayne C. Litzenberger wrote:
> I'm bringing this up again because the arguments I've seen in favour of
> fixing hasattr have been fairly weak, and I'd like to raise some stronger
> ones. Also, I haven't seen this issue considered specifically in the
> context of Python 3000.
The behavior of hasattr and (IIRC) isinstance and issubclass has been a
problem for several applications. For instance Zope requires code to
re-raise ConflictErrors. ZODB conflict errors must bubble through the
program flow until it hits the ZODB transaction system so it can re-roll
> I propose a few alternate behaviours for hasattr (and their consequences):
> 1. Swallow only AttributeError.
> - KeyboardInterrupt, SystemExit, and AssertionError are all passed
> through, solving all three of the above problems.
> - The behaviour of hasattr is made consistent with getattr(x,y,z).
I prefer 1) for Python 3.0
> 2. Swallow only Exception.
> - KeyboardInterrupt and SystemExit are passed through, but
> AssertionError is still swallowed.
> - Breaks less code than the previous option.
I think it's a sensible solution for Python 2.6.
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