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

   def add_at_beginning(self,my_data):  
      new_node = Node(my_data);  
      if self.head.data is None:  
       self.head = new_node;  
       self.tail = new_node;  
       new_node.next = self.head;  
      else:  
         temp = self.head;  
         new_node.next = temp;  
         self.head = new_node;  
         self.tail.next = self.head;
         
   def print_it(self):  
      curr = self.head;  
      if self.head is None:  
         print("这个列表是空的");  
         return;  
      else:  
         print(curr.data),  
         while(curr.next != self.head):  
            curr = curr.next;  
            print(curr.data),  
         print("\n");  
   
class circular_linked_list:  
   my_cl = list_creation()
   print("正在向列表中添加值")
   my_cl.add_at_beginning(21);  
   my_cl.print_it();  
   my_cl.add_at_beginning(53);  
   my_cl.print_it();  
   my_cl.add_at_beginning(76);
   my_cl.print_it(); 

正在向列表中添加值
21

53
21

76
53
21