Comparing strings from the back?

[Roy Smith]

In article <50485fca$0$29977$c3e8da3$5496439d at news.astraweb.com>,
 Steven D'Aprano <steve+comp.lang.python at pearwood.info> wrote:

> In any case, the *worst* case for string equality 
> testing is certainly O(N) (every character must be looked at), and the 
> *best* case is O(1) obviously (the first character fails to match).

The best case is O(0), if either string is empty (ducking and running).