import maya.api.OpenMaya as om
import maya.cmds as cmds

#Returns normal, tangent, at a given point on a curve, given the curve and a position in space.
#result as a list of openmaya MVector()
def getCurveNormal(mayaCurve, pos=[0,0,0]):
    selectionList = om.MSelectionList()
    selectionList.add(mayaCurve)
    dPath= selectionList.getDagPath(0)
    mCurve=om.MFnNurbsCurve (dPath)
    res=mCurve.closestPoint(om.MPoint(om.MVector(pos)),space=om.MSpace.kWorld)
    point=om.MVector(res[0])
    param=res[1]
    n=mCurve.normal(param,space=om.MSpace.kWorld)
    t=mCurve.tangent(param,space=om.MSpace.kWorld)
    li=[n,t,point]        
    return li