import Tkinter as tk


def main():
    global root

    root = tk.Tk()   # parent window


    message = tk.Label(root, text = "Hello World")
    message.pack()

    buttton = tk.Button(root, text="exit", command = buttonPushed)
    button.pack()

    tk.mainloop()


def buttonPushed():
    global root
    root.destroy()

main()

buttton = tk.Button(root, text="exit", command = buttonPushed(root))
button.pack()


def buttonPushed(root):
    root.destroy()

button = tk.Button(root, text="exit", command=root.destroy)

import Tkinter as tk

def main():

    root = tk.Tk()

    message = tk.Label(root, text="Hello World")
    message.pack()

    button = tk.Button(root, text="exit", command=root.destroy)
    button.pack()

    tk.mainloop()

main()

import Tkinter as tk

class interface(tk.Frame):
    def __init__(self, root):
        tk.Frame.__init__(self, root)

        self.root = root
        message = tk.Label(self.root, text = "Hello World")
        button = tk.Button(self.root, text="exit", command = self.buttonPushed)

        message.pack()
        button.pack()

    def buttonPushed(self):
        self.root.destroy()

root = tk.Tk()
inter = interface(root)
root.mainloop()