On Thu, Oct 2, 2014 at 6:27 PM, Sebastian Wagner <se...@sebix.at> wrote: > So, for non-structured arrays, the consens is an Exception. The question > is, which one. > AttributeError would be fully backwards compatible. Existing code checks > for the method and if it exists, the object has fields. > ValueError would make more sense, as the value - the array - is in wrong > format/structure/type.
If a non-structured array has its keys() raise AttributeError, I think that hasattr(arr, "keys") should return False, which implies that getattr(arr, "keys") should throw AttributeError. This would require that ndarray.__getattribute__ raise AttributeError, meaning "the attribute isn't here," not merely "the attribute doesn't have a value now." Otherwise people may rightly complain when they interrogate an array to see if it has keys(), find out that it does, but then get an error upon calling it which could have been known ahead of time. Now, to actually implement it this way would seem to require setting the "tp_getattro" function pointer (https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_getattro). Currently PyArray_Type has this field as null. If I understand everything correctly, adding a non-null function pointer here would mean some small runtime overhead to resolve every attribute on ndarray. I could easily be missing some detail which would allow us to do what I described above without a performance hit, but someone better versed would need to explain how/why. If I'm right about all that, and if the consensus is that keys() should raise an exception when dtype.names is None, then perhaps raising ValueError is the only viable option. I'd appreciate opinions from those experienced in the details of the C API. _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
