> On Jul 20, 2016, at 12:42 PM, Ian Kelly <ian.g.kelly at gmail.com> wrote: > > for i, n in reversed(enumerate(x)): pass > > fails with "TypeError: argument to reversed() must be a sequence". So make it a sequence: for i, n in reversed(list(enumerate(x))): pass If ``x`` is very large, you can use your zip/range technique to save memory.