python – Slow calculating sum of individual cells of matrix

I have a 3-D array in numpy, of dimensions 3000 x 2000 x 8

I need to modify the cells of the array so that each cell will contain the sum of all cells above and left of it, inclusive the current cell.

I am doing it using loops like below, but it is taking around 5 minutes to complete the program run. Is there a faster way in Python to achieve this (preferably without a loop)?

for depth in range(simg.shape(2)):
    for row in range(1,simg.shape(0)-1):
        for col in range(1,simg.shape(1)-1):