[Tutor] point and polygon

[Shi Mu]

why the following code report error?
"""
Is given point in polygon?
"""


def pointInPoly(point, pointsList):
        "Return True if point is contained in polygon (defined by
given list of points.)"

        assert len(pointsList) >= 3, 'Not enough points to define a
polygon (I require 3 or more.)'
        assert len(point) >= 2, 'Not enough dimensions to define a
point(I require 2 or more.)'

        # If given values are ints, code will fail subtly. Force them to floats.
        x,y = float(point[0]), float(point[1])
        xp = [float(p[0]) for p in pointsList]
        yp = [float(p[1]) for p in pointsList]

        # Initialize loop
        c=False
        i=0
        npol = len(pointsList)
        j=npol-1

        while i < npol:
                if ((((yp[i]<=y) and (y<yp[j])) or
                        ((yp[j]<=y) and(y<yp[i]))) and
                        (x < (xp[j] - xp[i]) * (y - yp[i]) / (yp[j] -
yp[i]) + xp[i])):
                        c = not c
                j = i
                i += 1

        return c


if __name__ == '__main__':
        print 'Simple pointInPoly() test...'

        pointA = (3,30)
        pointB = (8,8)
        poly = (-1,-1), (6,-1), (5,6), (0,5)

        assert pointInPoly(pointA, poly)
        assert not pointInPoly(pointB, poly)