Hello there. Please see my feature request: http://bugs.python.org/issue6326 The idea is to speed up the swapping of list elemenst so that a.swap(b) is equivalent to a[:], b[:] = b[:], a[:] but without all the overhead of creating slices, assigning them and so forth. In particular, it can help reduce the cost of creating instances of list subclasses, from raw lists: class mylist(list): def first(self): return self[0] m = mylist(source_list) This certainly creates m, but does so by copying source_list. If all we want to do is turn source_list into a mylist instance, it is much quicker to: m = mylist() m.swap(source_list) See the above issue for initial comments, especially concerns on how this can bypass all kind of insertion semantics of list subclasses. Cheers, Kristján