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

def add_data(head_ref,my_data):
   ptr_1 = Node(0)
   temp = head_ref
   ptr_1.data = my_data
   ptr_1.next = head_ref

   if (head_ref != None) :
      while (temp.next != head_ref):
         temp = temp.next
      temp.next = ptr_1
   else:
      ptr_1.next = ptr_1

   head_ref = ptr_1
   return head_ref

def count_node(head):
   temp = head
   result = 0
   if (head != None) :
      while True :
         temp = temp.next
         result = result + 1
         if (temp == head):
            break  
   return result

if __name__=='__main__':
   head = None
   head = add_data(head, 78)
   head = add_data(head, 56)
   head = add_data(head, 22)
   print("Elements are added to list")
   print("The number of nodes are : ")
   print(count_node(head))

元素已添加到列表中
节点数为：
3