#random lines, undraws old lines
import random
import time
from Tkinter import *
frmMain = Tk()
myCanvas = Canvas(width=400, height=400, background="orange")
oldx = 0
oldy = 0
while oldx <= 350:
    newx = random.randrange(1,401)
    newy = random.randrange(1,401)
    myCanvas.create_line(oldx,oldy,newx,newy,arrow="last")
    myCanvas.pack()
    myCanvas.update()
    time.sleep(1)
    myCanvas.create_line(oldx,oldy,newx,newy,fill="orange")
    oldx = newx
    oldy = newy


myCanvas.pack()
frmMain.mainloop()