>>> d = np.array(c)
>>> d
array([[ 1, 2, 3, 4, 5, 6, 7, 8, 9],
[11, 12, 13, 14, 15, 16, 17, 18, 19],
[21, 22, 23, 24, 25, 26, 27, 28, 29],
[31, 32, 33, 34, 35, 36, 37, 38, 39],
[41, 42, 43, 44, 45, 46, 47, 48, 49]])
>>> d[1,4]
15
切出一个列
>>> d[:,1]
array([ 2, 12, 22