np.stack

>>> np.stack((a, b), axis=-1)
array([[1, 2],
       [2, 3],
       [3, 4]])

>>> a = np.array([1, 2, 3])
>>> b = np.array([2, 3, 4])
>>> np.stack((a, b))
array([[1, 2, 3],
       [2, 3, 4]])