integral image for each depth in a three dimensional array

Hi all, I want to calculate integral images for each depth in a three dimensional array. My code is something like this: ret = np.empty(height, width, depth) int_imgs = [integral_image(image[:,:,i]) for i in range(depth)] for i in range(depth): ret[:,:,i] = int_imgs[i] Is there better way to do this? Thanks, masa