[python] матрица суммы элементов

>>> r = [[sum(matrix[i][:j]) for j in xrange(1, len(matrix) + 1)] for i in xrange(len(matrix))]
>>> r
[[0.1, 0.30000000000000004, 0.6000000000000001, 0.8, 1.0], 
[0.2, 0.4, 0.6000000000000001, 0.8, 1.0], 
[0.3, 0.5, 0.6, 0.8999999999999999, 0.9999999999999999], 
[0.4, 0.5, 0.7, 0.7999999999999999, 1.0], 
[0.2, 0.4, 0.6000000000000001, 0.9000000000000001, 1.0000000000000002]]