def ringIsClockwise(ringToTest):
    """
    determine if polygon ring coordinates are clockwise. clockwise signifies
    outer ring, counter-clockwise an inner ring or hole.
    """

    total = 0
    i = 0
    rLength = len(ringToTest)
    pt1 = ringToTest[i]
    pt2 = None
    for i in range(0, rLength - 1):
        pt2 = ringToTest[i + 1]
        total += (pt2[0] - pt1[0]) * (pt2[1] + pt1[1])
        pt1 = pt2

    return total >= 0