change swift-get-nodes ring_name = basename(ring_path)[:len('ring.gz')] to ring_name = basename(ring_path)[:-len('.ring.gz')] will resolve this problem.
change swift-get-nodes ring_name = basename( ring_path) [:len(' ring.gz' )] to ring_name = basename( ring_path) [:-len( '.ring. gz')] will resolve this problem.