Newbie Tkinter: how to quit window? (Win98, IDLE, Python 2.0b)

[Kirby Urner]

Studying 'Graphs & Charts' in 'Python and Tkinter Programming'
(pg 276 ff) and it looks to me like the code below should:

(a) put a window on screen with a Quit button under 
    400x400 canvas

(b) quit that window when Quit button is pressed

drawgraph() is in a module, and I'm launching it from 
IDLE, going:

 >>> import tkgraph
 >>> tkgraph.drawgraph()

So the window pops up.  When I hit Quit, I get the 
prompt back:

 >>>

in the IDLE Window, but the 400x400 canvas is still 
topmost -- didn't go away.  I have to hit the close 
box (X in upper right corner) to kill the Window.

This doesn't seem to be the behavior documented in
Tkinter class, which says quit method will cause all
widgets to be destroyed.

Whether documented or not, my question is, how to I
make the Quit button both return to IDLE _and_ 
get rid of the window.

=============================

# simple graphing -- tkgraph.py

# doesn't actually graph anything yet -- just testing 
# window behavior 

from Tkinter import *

def drawgraph():
    root = Tk()
    canvas = Canvas(root,height=400,width=400, bg='white')
    canvas.pack()
    Button(root,text='Quit',command=root.quit).pack()
    root.mainloop()