Passing null instead of empty collections is a practice that should be discouraged imho. There is an entire design pattern ("Null object" [1]) that's making the

Passing null instead of empty collections is a practice that should be discouraged imho. There is an entire design pattern ("Null object" [1]) that's making the point that you should use a "neutral" object instead. But it happens anyway sometimes, of course :)... in Python, I've also often used the `or` shortcut for that, like this for item in stuff or []: var_dump(item) or just at the top of the function, reassigning the function argument: stuff = stuff or [] [1] https://en.wikipedia.org/wiki/Null_object_pattern https://en.wikipedia.org/wiki/Null_object_pattern