import bpy

for obj in bpy.context.selected_objects:

    if obj.type == 'CURVE':

        print("is a curve")

        for spl in obj.data.splines:

            print("for each spline")

            for pnt in spl.bezier_points:

                print("for each point")

                print(pnt.tilt)

                pnt.tilt = 1.5708




                print(pnt.tilt)

                print("done")

            print("done")

        print("done")