Hi Zachary, I think your response highlights very well the apparent design flaw. Here is your response to my request for a use case where iteration over a matrix should yield matrices: do not iterate! Does some part of you not find that just a little bizarre?! As for offering as a use case that with a matrix M you are allowed to use M[0] instead of M[0,:] when you want the first row as a matrix, I really cannot take that trivial convenience seriously as the basis of a fundamental design decision. However there is no sympathy for my view on this, so I am not debating it any more. Instead I have asked a simple question: what use case is this design decision supporting? I am interested in this so that I can see into the decision better. Nowith Chris proposes that "M[i] == M[i,:] by definition". If so, that is an design-based answer to my question. I agree that M[i,:] should return a matrix. But my understanding was different: I thought M[i] relied on standard Python idexing while M[i,:] was numpy indexing. Cheers, Alan Isaac