Numpy References numpy arrays matrix = numpy.zeros([rows, columns]) Access using matrix[2,3] which will return the value in row 2 and column 3. sum of log probabilities scipy.misc.logsumexp() logsumexp([-2,-3]) = numpy.log(numpy.exp(-2) + numpy.exp(-3)) logsumexp(a, b) = log(e^a + e^b).