[beagle3]

There is a difference in semantics. Someone else might actually want os.path to change between call. The only problem is that the behavior of the idiomatic version is hard (almost impossible) to optimize, even though the more optimizable semantics are actually what most users want.

The language was designed with expressiveness in mind, and it often comes at the expense of speed. Lua and Nim seem to strike a much better balance, and even JavaScript if you avoid the performance killers like "with".

[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.