On 21 June 2013 19:57, Charles R Harris <charlesr.harris@gmail.com> wrote:

You could check the numpy/core/src/umath/test_rational.c.src code to see if you are missing something.

In v1.7+ the difference in behaviour between my code and the rational test case is because my scalar type doesn't subclass np.generic (aka. PyGenericArrType_Type). In v1.6 this requirement doesn't exist ... mostly ... In other words, it works as long as the supplied scalars are contained within a sequence. So: np.array([scalar]) => np.array([scalar], dtype=my_dtype) But: np.array(scalar) => np.array(scalar, dtype=object) For one of my scalar/dtype combos I can easily workaround the 1.7+ issue by just adding the subclass relationship. But another of my dtypes is wrapping a third-party type so I can't modify the subclass relationship. :-( So I guess I have three questions. Firstly, is there some cunning workaround when defining a dtype for a third-party type? Secondly, is the subclass-generic requirement in v1.7+ desirable and/or intended? Or just an accidental regression? And thirdly, assuming it's desirable to remove the subclass-generic requirement, would it also make sense to make it work for scalars which are not within a sequence? NB. If we decide there's some work which needs doing here, then I should be able to put time on it. Thanks, Richard