Tkinter destroy

import Tkinter as tk 
class MyWindow(object): 
    def __init__(self): 
        self.root = tk.Tk() 
        button=tk.Button(self.root, text='NEXT', command=self.OnNext) 
        button.pack() 

    def OnNext(self): 
        win = MyWindow() 
        self.root.destroy() 

win = MyWindow() 
win.root.mainloop()