numpy.concatenate()的官方语法是

numpy.concatenate（（a1，a2，...），axis = 0，out = None，dtype = None，cast =“ same_kind”

对out的要求是

out ndarray，可选
如果提供，则为放置结果的目的地。形状必须正确，并且与未指定out参数的串联连接的形状匹配。

举例

array01=np.arange(24).reshape(4,6)
array01

结果
array([[ 0,  1,  2,  3,  4,  5],
       [ 6,  7,  8,  9, 10, 11],
       [12, 13, 14, 15, 16, 17],
       [18, 19, 20, 21, 22, 23]])

array04 = np.ones((4,15),dtype='int32')
array04

结果
array([[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]])

np.concatenate((array01,array03),axis=1,out=array04)

结果
array([[ 0,  1,  2,  3,  4,  5,  0,  1,  2,  3,  4,  5,  6,  7,  8],
       [ 6,  7,  8,  9, 10, 11,  9, 10, 11, 12, 13, 14, 15, 16, 17],
       [12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26],
       [18, 19, 20, 21, 22, 23, 27, 28, 29, 30, 31, 32, 33, 34, 35]])