But you can never get people to use the new ABCs consistently.
Anyway, I'm not -1, I'm just -0 -- I don't think it'll make any difference
and you're better off just checking for __set__ (if it only has __set__ but
not __get__, do you care what it is?).
On Tue, Jan 17, 2017 at 10:18 AM, Roberto Martínez <
robertomartin...@gmail.com> wrote:
> Well, for me having to check both __get__ and __str__ for a data
> descriptor feels inelegant.
>
> After read the documentation of collections.abc again "This module
> provides abstract base classes that can be used to test whether a class
> provides a particular interface; for example, whether it is hashable or
> whether it is a mapping." I ask: what is the criteria to decide which
> interfaces are worth implemented as an ABC in the standard library?
>
> To my understanding, any well defined python protocol should have a proper
> ABC.
>
> El mar., 17 ene. 2017 a las 18:55, Guido van Rossum (<gu...@python.org>)
> escribió:
>
>> For this use case I see nothing wrong with hasattr(myobj, '__set__').
>>
>> On Tue, Jan 17, 2017 at 9:41 AM, Roberto Martínez <
>> robertomartin...@gmail.com> wrote:
>>
>> I need to check if some objects obey the descriptor protocol in the
>> construction of a metaclass. I expect to be able to write something like:
>>
>> if isinstance(myobj, abc.DataDescriptor):
>> # do something
>>
>> The other idea crossing my mind is something like:
>>
>> if all(hasattr(myobj, attr) for attr in ('__get__', '__set__')):
>> # do something
>>
>>
>> El mar., 17 ene. 2017 a las 18:07, Guido van Rossum (<gu...@python.org>)
>> escribió:
>>
>> Well, these are an example of the purest duck typing. Just implement
>> __get__ and/or __set__ (and __delete__) and you're good.
>>
>> What's the situation where you miss them?
>>
>> --Guido
>>
>> On Tue, Jan 17, 2017 at 8:51 AM, Roberto Martínez <
>> robertomartin...@gmail.com> wrote:
>>
>> Hi,
>>
>> I miss abstract base classes in collections.abc implementing the
>> descriptor protocol. Any reason why they do not exist?
>>
>> What do you think of adding NonDataDescriptor and DataDescriptor ABCs?
>>
>> Best regards,
>> Roberto
>>
>> _______________________________________________
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>>
>>
>>
>>
>> --
>> --Guido van Rossum (python.org/~guido)
>>
>>
>>
>>
>> --
>> --Guido van Rossum (python.org/~guido)
>>
>
--
--Guido van Rossum (python.org/~guido)
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