old_contents: #!/usr/bin/python
  
  def f():
      '''
      this is comment
      '''
      name = "guy"
      print 'hello %s' %  (name)
  
  
  if __name__ == '__main__':
      f()
  
  
  
  
new_contents: #!/usr/bin/python
  #from twisted.internet import reactor
  import traceback
  
  def hello():
      print "hello!"
      traceback.print_stack()
  
  
  def test():
      from twisted.internet import reactor
      reactor.callWhenRunning(hello)
      reactor.run()
  
  
  
  if __name__ == '__main__':
      test()
  
  
  
  
subject: add main.py