[cwyers]

> Someone else might actually want os.path to change between call.

Who? Why?

[fovc]

The os.path is not a great example, but imagine a loop where inside the body you mutate some state of an instance and then directly access it. Compare the following with the os.path example:

  for animal in circus.animals:
      circus.next_free_clown.assign(animal)
      # circus.next_free_clown changes in every iteration

[zardeh]

Monkeypatching for debugging, mocking, etc.

Most of those are rare, but feasible. Monkeypatching a global as a side effect even rarer, but I think I've done it at some point.