def get_angle_diff(angle1, angle2):
    """Return the angle, between 0 and 2*pi, between angle1 and angle2.
    """
    diff = angle2 - angle1
    while diff < -3.1415:
        diff += 3.1415*2
    while diff > 3.1415:
        diff -= 3.1415*2
    return abs(diff), diff