numpy.roll

numpy.roll(a, shift, axis=None)

Roll array elements along a given axis.

Elements that roll beyond the last position are re-introduced at the first.

Parameters :

a : array_like

Input array.

shift : int

The number of places by which elements are shifted.

axis : int, optional

The axis along which elements are shifted. By default, the array is flattened before shifting, after which the original shape is restored.

Returns :

res : ndarray

Output array, with the same shape as a.

See also

rollaxis

Roll the specified axis backwards, until it lies in a given position.

Examples

>>> x = np.arange(10)
>>> np.roll(x, 2)
array([8, 9, 0, 1, 2, 3, 4, 5, 6, 7])

>>> x2 = np.reshape(x, (2,5))
>>> x2
array([[0, 1, 2, 3, 4],
       [5, 6, 7, 8, 9]])
>>> np.roll(x2, 1)
array([[9, 0, 1, 2, 3],
       [4, 5, 6, 7, 8]])
>>> np.roll(x2, 1, axis=0)
array([[5, 6, 7, 8, 9],
       [0, 1, 2, 3, 4]])
>>> np.roll(x2, 1, axis=1)
array([[4, 0, 1, 2, 3],
       [9, 5, 6, 7, 8]])