こんな感じですか?
Python
1M,N = 6,8
2data = [[j for j in range(i,i+N)] for i in range(0,M*N,N)]
3
4x0,x1,y0,y1 = 1,3,1,2
5data_range = [d[x0:x0+x1] for d in data[y0:y0+y1]]
6# -> [[9, 10, 11], [17, 18, 19]]
7
8total = sum([sum(d) for d in data_range])
9# -> 84
Numpyを使うともう少しシンプルになります。
Python
1import numpy as np
2
3M,N = 6,8
4data = np.reshape(np.arange(M*N), (M, N))
5
6x0,x1,y0,y1 = 1,3,1,2
7data_range = data[y0:y0+y1, x0:x0+x1]
8
9total = data_range.sum()