Linked List Background

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

# Class to create a Linked List
class LinkedList(object):
	def __init__(self, head=None):
		self.head = head

	# Search an element and print its index
	def search(self, head, data, index):
		if head.data == data:
			print (index)
		else:
			# Make recursive calls
			if head.next:
				return self.search(head.next, data, index+1)
			else:
				raise ValueError("Node not in linked list")

	# Print the linked list
	def print_list(self):
		if self.head == None:
			raise ValueError("List is empty")

		current = self.head 
		while(current):
			print (current.data, end="  ")
			current = current.next
		print ('\n')

	# Find length of Linked List
	def size(self):
		if self.head == None:
			return 0

		size = 0
		current = self.head
		while(current):
			size += 1
			current = current.next

		return size

	# Insert a node in a linked list
	def insert(self, data):
		node = Node(data)
		if not self.head:
			self.head = node
		else:
			node.next = self.head
			self.head = node

	# Delete a node in a linked list
	def delete(self, data):
		if not self.head:
			return
		
		temp = self.head
		
		# Check if head node is to be deleted
		if head.data == data:
			head = temp.next
			print ("Deleted node is " + str(head.data))
			return

		while(temp.next):
			if (temp.next.data == data):
				print ("Node deleted is " + str(temp.next.data))
				temp.next = temp.next.next
				return
			temp = temp.next
		print ("Node not found")
		return

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

    def addNodeLast(self, val):
        current = self.head
        while current.next != None:
            current = current.next
        newNode = Node(val)
        current.next = newNode
        newNode.prev = current
        self.tail = newNode

    def insertNode(self, val, newVal):
        if self.tail.value == val:
            self.addNodeLast(newVal)
        elif self.head.value == val:
            newNode = Node(newVal)
            newNode.next = self.head.next
            newNode.prev = self.head
            newNode.next.prev = newNode
            self.head.next = newNode
        else:
            current = self.head.next
            while current.value != val:
                current = current.next
            newNode = Node(newVal)
            newNode.next = current.next
            newNode.next.prev = newNode 
            newNode.prev = current
            current.next = newNode

    def removeNode(self, val):
        if self.head.value == val:
            self.head = self.head.next
            self.head.prev = None
        elif self.tail.value == val:
            self.tail = self.tail.prev
            self.tail.next = None
        else:
            current = self.head.next
            while current.value != val:
                current = current.next
            current.prev.next = current.next
            current.next.prev = current.prev

    def showReverse(self):
        current = self.tail
        while current != None:
            print(current.value)
            current = current.prev

    def show(self):
        current = self.head
        while current != None:
            print(current.value)
            current = current.next