Bill Spotz is the lead developer of PyTrilinos, a python interface to Trilinos. The Trilinos Project, developed at Sandia National Laboratories, is a collection of object-oriented C++ packages that can be used together to solve large-scale linear, nonlinear, and eigen problems. The PyTrilinos interface is compatible with NumPy.

Bill also contributed numpy.i to the NumPy distribution. For developers who use the Simple Wrapper and Interface Generator (or SWIG) to provide python interfaces to C or C++ code, numpy.i provides a mechanism for using python sequences and NumPy arrays to provide buffers of data to the underlying C/C++ code.

Bill also first proposed that 1D objects extracted from a matrix object should be of new types: row_vector and col_vector. This has sparked some spirited debate, to say the least. See ConjugateGradientExample for some discussion.