import rhinoscriptsyntax as rs
def PlanarSurfaceNormal(srf):
domU=rs.SurfaceDomain(srf,0)
domV=rs.SurfaceDomain(srf,1)
return rs.SurfaceNormal(srf,[domU[0],domV[0]])
srf1=rs.GetObject("Select first surface",rs.filter.surface)
srf2=rs.GetObject("Select second surface",rs.filter.surface)
if rs.IsSurfacePlanar(srf1) and rs.IsSurfacePlanar(srf2):
normVec1=PlanarSurfaceNormal(srf1)
normVec2=PlanarSurfaceNormal(srf2)
angle=rs.VectorAngle(normVec1,normVec2)
print "The angle between surfaces is {} degrees".format(angle)