Hello Aiping,
Bellow is a small example which might help you.
import s4l_v1 as s4l
import XCoreModeling
import random
radius = 0.1
points = list()
for ii in range(20):
points.append(s4l.Vec3(random.randrange(0,20), random.randrange(0,20), random.randrange(0,20)))
spline = XCoreModeling.CreateSpline(points)
wire = XCoreModeling.ThickenWire(spline, radius)
Regards,
Spuky