I am one the authors of 'cvxopt', a Python package that includes simple matrix classes aimed at numerical linear algebra for convex solvers, and I saw the discussion on the list regarding interfacing to such classes. I think the idea of an advanced interface or buffer protocol to exchange information between simple array types without using (or knowing) the API of the different classes is great. What is the status of the new array interface? When it is ready for testing, I will definitely try it out. - Joachim