I was wondering whether there's an on-screen keyboard available when there's no keyboard connected (in tablet mode). If so, does that work adequately?

Hynek Černoch Maybe it would be better to use this quite different function as an inline flatten, very much like list.sort() or list.remove(). The return value is then always None and the list will be replaced by the flattened version. That can be implemented like: def flatten_inplace ( lst ): build = [] while lst: e = lst.pop() if isinstance(e, list): lst.extend(e) else : build.append(e) lst.extend(build[:: -1 ])

Hynek Černoch Good point. It is true that the original list will be destroyed. But if that doen't matter a deep copy is not required.

Here's a different, non recursive, solution for deep flattening: def flatten ( bad ): good = [] while bad: e = bad.pop() if isinstance(e, list): bad.extend(e) else : good.append(e) return good[:: -1 ] Very likely quite fast as well.