Comment by kstrauser

Then I don’t know what you mean. If you have:

  foo = open(‘bar.txt’)
  answer = frobnicate(foo)
  print(foo)

then frobnicate may call foo.close(), or it may read foo’s contents so that you’d have to seek back to the beginning before you could read them a second time. There’s literally nothing you can do in frobnicate that can make it such that the 3rd raises a NameError because foo no longer exists.