import numpy as np

im = [
    [1,2,3],
    [4,5,6]
]
im = np.array(im)
im_row = np.cumsum(im, axis=1)
# satirlar dogrultusunda kumulatif toplam
print im_row
# [[ 1  3  6]
# [ 4  9 15]

# sutunlar dogrultusunda kumulatif toplam
im_col = np.cumsum(im, axis=0)
print im_col
# [[1 2 3]
# [5 7 9]]