class object using widget

[Jeff Schwab]

asit wrote:
> from Tkinter import *                          # get widget classes
> from tkMessageBox import askokcancel           # get canned std dialog
> 
> class Quitter(Frame):                          # subclass our GUI
>     def __init__(self, parent=None):           # constructor method
>         Frame.__init__(self, parent)
>         self.pack()
>         widget = Button(self, text='Quit', command=self.quit)
>         widget.pack(side=LEFT)
>     def quit(self):
>         ans = askokcancel('Verify exit', "Really quit?")
>         if ans: Frame.quit(self)
> 
> if __name__ == '__main__':  Quitter().mainloop()
> 
> In the above program, why the error comes ??

What error?