code: def scan_items(self):
          
          for m, s in self.redis.zscan_iter(self.key):
              yield self._unpickle(m), s
docs: Yield each of the ``(member, score)`` tuples from the collection,
          without pulling them all into memory.
  
          .. warning::
              This method may return the same (member, score) tuple multiple
              times.
              See the `Redis SCAN documentation
              <http://redis.io/commands/scan#scan-guarantees>`_ for details.