hello.py

# Display hello, world in a button; clicking it quits the program

import sys
from Tkinter import *

def main():
	root = Tk()
	button = Button(root)
	button['text'] = 'Hello, world'
	button['command'] = quit_callback	# See below
	button.pack()
	root.mainloop()

def quit_callback():
	sys.exit(0)

main()