>>> M
[[1, 2, 3], [4, 5, 6], [7, 8, 9]]
>>> N
[[2, 2, 2], [3, 3, 3], [4, 4, 4]]
>>> M[1]
[4, 5, 6]
>>> M[1][2]
6
>>> [row[1] for row in M]
[2, 5, 8]
>>> [M[row][1] for row in (0,1,2)]
[2, 5, 8]
>>> [M[i][i] for i in range(len(M))]
[1, 5, 9]
>>> [M[row][col]*N[row][col] for row in range(3) for col in range(3)]
[2, 4, 6, 12, 15, 18, 28, 32, 36]
>>> [[M[row][col]*N[row][col] for row in range(3)]for col in range(3)]
[[2, 12, 28], [4, 15, 32], [6, 18, 36]]
>>>
