import rhinoscriptsyntax as rs
import Rhino.Geometry
import scriptcontext

def PlaneCurveIntersection(plane, curve, tolerance=rs.UnitAbsoluteTolerance()):
    "Intersect an infinite plane and a curve object"
    plane = rs.coerceplane(plane, True)
    curve = rs.coercecurve(curve, True)
    if tolerance is None: tolerance = scriptcontext.doc.ModelAbsoluteTolerance
    intersections = Rhino.Geometry.Intersect.Intersection.CurvePlane(curve, plane, tolerance)
    if intersections:
        rc = []
        for intersection in intersections:
            a = 1
            if intersection.IsOverlap: a = 2
            b = intersection.PointA
            c = intersection.PointA2
            d = intersection.PointB
            e = intersection.PointB2
            f = intersection.ParameterA
            g = intersection.ParameterB
            h = intersection.OverlapA[0]
            i = intersection.OverlapA[1]
            j = intersection.OverlapB[0]
            k = intersection.OverlapB[1]
            rc.append( (a,b,c,d,e,f,g,h,i,j,k) )
    else: rc = None
    return rc
a = rs.GetObject()     
rs.SelectObject(a)

b = PlaneCurveIntersection(rs.WorldZXPlane(), a)
rs.AddPoint(b[0][3])