[Python-Dev] 'hasattr' is broken by design (original) (raw)

P.J. Eby pje at telecommunity.com
Tue Aug 24 00:45:32 CEST 2010

At 06:12 PM 8/23/2010 -0400, Yury Selivanov wrote:

BTW, is it possible to add new magic method hasattr? Maybe not in Python 3.2, but in general.

In order to do this properly, you'd need to also add has or exists (or some such) to the descriptor protocol; otherwise you break descriptors' ability to operate independently of the class they're used in. You would probably also need a hasattribute, in order to be able to properly synchronize with getattr/getattribute.

Seems like overkill to me, though, as I'm not sure how such a protocol actually helps ORM or persistence schemes (and I've written a few). Pretty much, if you're trying to check for the existence of an attribute, you're probably about to be getting that attribute anyway. (i.e. why query the existence of an attribute you don't intend to use?)

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