Tk Menu click event error

Scripting Issues
1 
import direct.directbase.DirectStart
from Tkinter import *

root = base.tkRoot

def hello():
    print "hello!"

# create a toplevel menu
menubar = Menu(root)
menubar.add_command(label="Hello!", command=hello)
menubar.add_command(label="Quit!", command=root.quit)

# display the menu
root.config(menu=menubar)

base.startTk()

run()

(I use panda3d-1.8.0).

When I click on menu item, a run-time error popups. It looks like:

2

[SOLVED] I use wxpython instead.