[Python-Dev] 'hasattr' is broken by design

[Tres Seaver]

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Guido van Rossum wrote:
> On Mon, Aug 23, 2010 at 7:46 AM, Benjamin Peterson <benjamin at python.org> wrote:
>> 2010/8/23 Yury Selivanov <yselivanov at gmail.com>:
>>> 1) I propose to change 'hasattr' behaviour in Python 3, making it to swallow only AttributeError exceptions (exactly like 'getattr').  Probably, Python 3.2 release is our last chance.
>> I would be in support of that.
> 
> I am cautiously in favor. The existing behavior is definitely a
> mistake and a trap. But it has been depended on for almost 20 years
> now.
> 
> I recommend that you create a patch, apply it, run the *entire* stdlib
> test suite and see how much breaks. That will give you an idea of the
> damage to expect for 3rd party code.

Robust third-party code is written to avoid 'hasattr', for precisely
this reason.  Third-party code which relies on 'hasattr' to mask
non-AttributeErrors is broken alreay (it just doesn't show the borkedness).


Tres.
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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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