[xamuel]

There isn't even any guarantee that "os.path" is the vanilla iterative lookup it's presented as. For all we know, it could be a @property-decorated method thousands of lines long.

[beagle3]

But as long as you know it is the same thing, you could move ("hoist") it outside the loop. In Lua, you generally can (and LuaJIT2 does). In Python, rarely if ever.

[smhx]

and that's when you dont do the optimization.