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

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

   def add_vals(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 print_it(self):
      curr = self.head
      while curr:
         print(curr.data)
         curr = curr.next

   def count_elem(self, key):
      curr = self.head
      count_val = 0
      while curr:
         if curr.data == key:
            count_val = count_val + 1
         curr = curr.next
      return count_val

my_instance = LinkedList_structure()
my_list = [56, 78, 98, 12, 34, 55, 0]
for elem in my_list:
   my_instance.add_vals(elem)
print('链表是：')
my_instance.print_it()

key_val = int(input('输入数据：'))
count_val = my_instance.count_elem(key_val)
print('{0}在列表中出现了{1}次。'.format(key_val, count_val))

链表是：
56
78
98
12
34
55
0
输入数据：0
0在列表中出现了1次。