def by_row(array_2d, array_3d):
    """
    Iterates through each row filling in values from the 2d array to the 3d array

    :param array_2d:    2D Array 9x9
    :param array_3d:    3D Array 9x9x9
    :return:            array_3d
    """
    for col in range(9):
        for row in range(9):
            value = array_2d[col][row]
            if value == 0:
                pass
            else:
                for depth in range(9):
                    array_3d[col][depth][value-1] = value

    return array_3d