numpy拼接数组之vstack，hstack

hstack是水平方向拼接数组
vstack是垂直方向拼接数组
拼接顺序是参数的输入顺序，如a,b,c三个数组，np.vstack((a,b,c))就是按照abc的顺序垂直拼接

a = np.array([[1,2,3], [3,2,1]])
b = np.array([[4,5,6], [6,5,4]])
c = np.array([[7,8,9], [9,8,7]])
print(np.hstack((a,b,c)))
print(np.vstack((a,b,c)))

>> array([[1, 2, 3, 4, 5, 6, 7, 8, 9],
        [3, 2, 1, 6, 5, 4, 9, 8, 7]])
>>>array([[1, 2, 3],
       [3, 2, 1],
       [4, 5, 6],
       [6, 5, 4],
       [7, 8, 9],
       [9, 8, 7]])