Hi Sylvain, Thanks for getting in touch! The traitlets library sounds interesting, and provides good additional evidence that this is a capability that folks are interested in having available.
On 20 July 2016 at 15:26, Sylvain Corlay <sylvain.cor...@gmail.com> wrote: > My understanding is that the proposed __set_name__ in PEP487 exactly > corresponds to our class_init, although interestingly we often do much more > in class_init than setting the name of the descriptor, such as setting a > this_class attribute or calling class_init on contained descriptors. > Therefore I do not think that the names __set_name__ or __set_owner__ are > appropriate for this use case. > > In a way, the long-form explicit names for our class_init and instance_init > methods would be something like __init_fom_owner_class__, and > __touch_instance__. It's certainly a reasonable question/concern, but we've learned from experience that we're better off using protocol method names that are very specific to a particular intended use case, even if they can be adapted for other purposes. The trick is that we want educators teaching Python to be able to very easily answer the question of "What is this special method for?" (even if they later go on to say "And it's also used for these other things...") One previous example of that is the __index__ protocol, where the actual semantics are "instances of this type can be losslessly converted to integers", but the protocol is named for the particular use case "instances of this type can be used as sequence indices". For PEP 487, the two operations guiding the naming of the methods are "notify a base class when a new subclass is defined" and "notify a descriptor of its attribute name when assigned to a class". The precise verbs then mirror those already used in other parts of the related protocols (with __init__ leading to __init_subclass__, and __set__ leading to __set_name__). The main capability that __set_name__ provides that was previously difficult is letting a descriptor know its own name in the class namespace. The fact a descriptor implementor can do anything else they want as a side-effect of that new method being called isn't substantially different from the ability to add side-effects to the existing __get__, __set__ and __delete__ protocol methods. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
