print(np.array([xx.ravel(), yy.ravel()]).T)
#---------------------------------------------------
#array([[0, 0],
#       [1, 0],
#       [2, 0],
#       [0, 1],
#       [1, 1],
#       [2, 1],
#       [0, 2],
#       [1, 2],
#       [2, 2]])
#---------------------------------------------------