class Node:
   def __init__(self, data):
      self.data = data
      self.next = None

class LinkedList_struct:
   def __init__(self):
      self.head = None
      self.last_node = None

   def add_elements(self, data):
      if self.last_node is None:
         self.head = Node(data)
         self.last_node = self.head
      else:
         self.last_node.next = Node(data)
         self.last_node = self.last_node.next

def convert_to_circular_list(my_list):
   if my_list.last_node:
      my_list.last_node.next = my_list.head

def last_node_points(my_list):
   last = my_list.last_node
      if last is None:
         print('链表为空...')
         return
      if last.next is None:
         print('最后一个节点指向空...')
      else:
         print('最后一个节点指向元素，它有 {} ...'.format(last.next.data))

my_instance = LinkedList_struct()

my_input = input('输入链接列表的元素... ').split()
for data in my_input:
   my_instance.add_elements(int(data))

last_node_points(my_instance)

print('链接列表正在转换为循环链接列表...')
convert_to_circular_list(my_instance)

last_node_points(my_instance)

输入链接列表的元素... 56 32 11 45 90 87
最后一个节点指向空...
链接列表正在转换为循环链接列表...
最后一个节点指向元素，它有 56 ...