# Python - Insert a new node at the start of the Circular Doubly Linked List

In this method, a new node is inserted at the start of the circular doubly linked list. For example - if the given List is 10->20->30 and a new element 100 is added at the start, the List becomes 100->10->20->30.

Inserting a new node at the start of the circular doubly linked list is very easy. First, a new node with given element is created. It is then added at the start of the list by linking the head node and last node to the new node.

The function *push_front* is created for this purpose. It is a **6-step process**.

def push_front(self, newElement): #1 & 2 & 3. allocate node, assign data element # assign null to the next and prev of # the new node newNode = Node(newElement) #4. Check the list is empty or not, # if empty make the new node as head if(self.head == None): self.head = newNode newNode.next = self.head newNode.prev = self.head return else: #5. Else, traverse to the last node temp = self.head while(temp.next != self.head): temp = temp.next #6. Adjust the links temp.next = newNode newNode.prev = temp newNode.next = self.head self.head.prev = newNode self.head = newNode

The below is a complete program that uses above discussed concept to insert new node at the start of the circular doubly linked list.

# node structure class Node: def __init__(self, data): self.data = data self.next = None self.prev = None #class Linked List class LinkedList: def __init__(self): self.head = None #Add new element at the start of the list def push_front(self, newElement): newNode = Node(newElement) if(self.head == None): self.head = newNode newNode.next = self.head newNode.prev = self.head return else: temp = self.head while(temp.next != self.head): temp = temp.next temp.next = newNode newNode.prev = temp newNode.next = self.head self.head.prev = newNode self.head = newNode #display the content of the list def PrintList(self): temp = self.head if(temp != None): print("\nThe list contains:", end=" ") while (True): print(temp.data, end=" ") temp = temp.next if(temp == self.head): break else: print("\nThe list is empty.") # test the code MyList = LinkedList() #Add three elements at the start of the list. MyList.push_front(10) MyList.push_front(20) MyList.push_front(30) MyList.PrintList()

The above code will give the following output:

The list contains: 30 20 10