Travis E. Oliphant wrote: >> Travis, >> >> You have been getting mostly objections so far; > I wouldn't characterize it that way, but yes 2 people have pushed back a > bit, although one not directly speaking to the proposed behavior. > > The issue is that [] notation does more than just "select from a > container" for NumPy arrays. In particular, it is used to reshape an > array to more dimensions: [..., newaxis] > > A common pattern is to reduce over a dimension and then re-shape the > result so that it can be combined with the un-reduced object. > Broadcasting makes this work if the dimension being reduced along is the > first dimension. But, broadcasting is not enough if you want the > reduction dimension to be arbitrary: > > Thus, > > y = add.reduce(x, axis=-1) produces an N-1 array if x is 2-d and a > numpy scalar if x is 1-d.
Why does it produce a scalar instead of a 0-d array? Wouldn't the latter take care of your use case, and be consistent with the action of reduce in removing one dimension? I'm not opposed to your suggested change--just trying to understand it. I'm certainly sympathetic to your use case, below. I dimly recall extensive and confusing (to me) discussions of numpy scalars versus 0-d arrays during your heroic push to make numpy gel, and I suspect the answer is somewhere back in those discussions. Eric > > Suppose y needs to be subtracted from x. > > If x is 2-d, then > > >>> x - y[...,newaxis] > > is the needed code. But, if x is 1-d, then > > >>> x - y[..., newaxis] > > returns an error and a check must be done to handle the case > separately. If y[..., newaxis] worked and produced a 1-d array when y > was a numpy scalar, this could be avoided. > > > -Travis O. > > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
