current_users = ["Niuniu","Niumei", "GURR", "LOLO"] for m in range(0,4): current_users[m]=current_users[m].lower() new_users=["GurR","Niu Ke Le","LoLo","Tuo Rui Chi"] for x in range(0,4): if new_users[x].lower() in current_users: print("The user name %s has already been registered! Please change it...