请教一个关于TK的问题

CODE:

#!/usr/bin/env python
from Tkinter import *
root=Tk()
frame=Frame(root)
frame.pack()
# Button quit
button = Button(frame, text="QUIT", fg="red", command=frame.quit)
button.pack(side=LEFT)
# fun sayhi
def sayhi():
        newroot = Tk()
        window = Label(newroot,text="I say hi in new window")
        window.pack()
        newroot.mainloop()
# hi button
hib = Button(frame,text="say hi",command=sayhi)
hib.pack(side=LEFT)
root.mainloop()