Link List

class Node:
  def __init__(self, value):
    self.next = None
    self.prev = None
    self.val = value

class DaubleLinkList:
  def __init__(self):
    self.head = None
    self.tail = None
    self.size = 0

  def add(self, val):
    node = Node(val)
    if self.tail is None:
      self.head = node
      self.tail = node
      self.size += 1

    else:
      self.tail.next = node
      node.prev = self.tail
      self.tail = node
      self.size += 1

  def __str__(self):
    vals = []
    node = self.head
    while node is not None:
      vals.append(node.val)
      node = node.next

    return str(vals)


mylist = DaubleLinkList()
mylist.add(5)
mylist.add(2)

mylist.add(4)
mylist.add(4)
mylist.add(4)

print(mylist)
print(mylist.size)