On 11/01/2010 21:12, Nick Coghlan wrote:
Benjamin Peterson wrote:
> My question is: Is this a doc bug or a implementation bug? If the
former, it will be the description of a data descriptor much less
consistent, since it will require that a __get__ method be present,
too. If the latter, the fix may break some programs relying on the
ability to "cache" a value in the instance dictionary.
[1] http://docs.python.org/reference/datamodel#invoking-descriptors
[snip...]
Note that the behaviour here is still different from that of a data
descriptor: with a data descriptor, once it gets shadowed in the
instance dictionary, the descriptor is ignored *completely*. The only
way to get the descriptor involved again is to eliminate the shadowing.
The non-data descriptor with only __set__ is just choosing not to
override the attribute lookup process.
Does that mean we need a third class of descriptors that are neither
data descriptors nor non-data descriptors?
What should we call them: really-not-data-descriptors?
All the best,
Michael
Cheers,
Nick.
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