Not much love for curve weight in R6

http://developer.rhino3d.com/api/RhinoCommonWin/html/M_Rhino_Geometry_NurbsCurve__ctor_1.htm

You have to add the weights separately… rhinoscriptsyntax AddNurbsCurve()

def AddNurbsCurve(points, knots, degree, weights=None):
    """Adds a NURBS curve object to the document
    Parameters:
      points = list containing 3D control points
      knots = Knot values for the curve. The number of elements in knots must
          equal the number of elements in points plus degree minus 1
      degree = degree of the curve. must be greater than of equal to 1
      weights[opt] = weight values for the curve. Number of elements should
          equal the number of elements in points. Values must be greater than 0
    """
    points = rhutil.coerce3dpointlist(points, True)
    cvcount = len(points)
    knotcount = cvcount + degree - 1
    if len(knots)!=knotcount:
        raise Exception("Number of elements in knots must equal the number of elements in points plus degree minus 1")
    if weights and len(weights)!=cvcount:
        raise Exception("Number of elements in weights should equal the number of elements in points")
    rational = (weights!=None)
    
    nc = Rhino.Geometry.NurbsCurve(3,rational,degree+1,cvcount)
    for i in xrange(cvcount):
        cp = Rhino.Geometry.ControlPoint()
        cp.Location = points[i]
        if weights: 
            cp.Weight = weights[i]
        else:
            cp.Weight = 1.0
        nc.Points[i] = cp
    for i in xrange(knotcount): nc.Knots[i] = knots[i]
    rc = scriptcontext.doc.Objects.AddCurve(nc)
    if rc==System.Guid.Empty: raise Exception("Unable to add curve to document")
    scriptcontext.doc.Views.Redraw()
    return rc