def diff_pos(initial, target):
    """ Return the move required to move from one position to another.

    Will return the move required to transition from `initial` to `target`. If
    `initial` equals `target` this is `stop`.

    Parameters
    ----------
    initial : tuple of (int, int)
        the starting position
    target : tuple of (int, int)
        the target position

    Returns
    -------
    move : tuple of (int, int)
        the resulting move

    """
    return (target[0]-initial[0], target[1]-initial[1])