Doubly Linked List Python

 

# singly linked list

class Node:

  def __init__(self,data):

    self.data = data

    self.prev = None

    self.next = None

class dl:

  def __init__(self):

    self.head = None

    self.tail = None

 

  def is_empty(self):

    return self.head is None

 

  def insertb(self,value):

    new_node = Node(value)

    if self.is_empty():

      self.head = self.tail = new_node

    else:

      new_node.next = self.head

      self.head.prev = new_node

      self.head = new_node

 

  def inserte(self,value):

    new_node = Node(value)

    if self.is_empty():

      self.head = self.tail = new_node

    else:

      new_node.prev = self.tail

      self.tail.next = new_node

      self.tail = new_node

 

  def forward(self):

    current = self.head

    while current:

      if current.data != None:

        print(current.data,'<->',end='')

      current = current.next

    print()

  def backward(self):

    current = self.tail

    while current:

      if current.data != None:

        print(current.data,'<->',end='')

      current = current.prev

    print()

  def delete(self,value):

    current = self.head

    while current:

      if current.data != None and current.data == value:

        current.data = None

      current = current.next

    print("deleted...")

    self.forward()

    self.backward()

    self.size()

 

  def update(self,value,replace):

    current = self.head

    while current:

      if current.data != None and current.data == value:

        current.data = replace

      current = current.next

    print("updated...")

    self.forward()

    self.backward()

   

  def size(self):

    current = self.head

    size=0

    while current:

      if current.data != None :

        size += 1

      current = current.next

    print(f"size is {size}...!")

 

l = dl()

l.insertb(1)

l.insertb(2)

l.insertb(3)

l.inserte(4)

l.inserte(5)

l.delete(1)

l.update(2,22)