import numpy as np
L = np.asarray([[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12], [13, 14, 15], [16, 17, 18]])
L.reshape(1, 6, 3)
# Output:
array([[[ 1, 2, 3],
[ 4, 5, 6],
[ 7, 8, 9],
[10, 11, 12],
[13, 14, 15],
[16, 17, 18]]])
Понятия не имею, зачем ты это делаешь ...