# Python - Delete the first node of the Circular Doubly Linked List

In this method, the first node of the circular doubly linked list is deleted. For example - if the given list is 10->20->30->40 and the first node is deleted, the list becomes 20->30->40.

Deleting the first node of the circular doubly linked list is very easy. If the list contains one node, delete the node. If the list contains more than one node, then create two nodes - temp and firstNode both pointing to the head. Using temp node, traverse to the last node of the list. Make next of head as the head node and update all links. Finally, delete the first node.

The function *pop_front* is created for this purpose. It is a **4-step process**.

def pop_front(self): if(self.head != None): #1. the list contains one node, delete # make the head null if(self.head.next == self.head): self.head = None else: #2. if the list contains more than one node, # create two nodes - temp and firstNode, both # pointing to head node temp = self.head firstNode = self.head #3. using temp node, traverse to the last node while(temp.next != self.head): temp = temp.next #4. Make head as next of head, and # update links self.head = self.head.next self.head.prev = temp temp.next = self.head firstNode = None

The below is a complete program that uses above discussed concept of deleting the first node of the circular doubly linked list.

# node structure class Node: def __init__(self, data): self.data = data self.next = None self.prev = None #class LinkedList class LinkedList: def __init__(self): self.head = None #Add new element at the end of the list def push_back(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.next = self.head newNode.prev = temp self.head.prev = newNode #Delete first node of the list def pop_front(self): if(self.head != None): if(self.head.next == self.head): self.head = None else: temp = self.head firstNode = self.head while(temp.next != self.head): temp = temp.next self.head = self.head.next self.head.prev = temp temp.next = self.head firstNode = None #display the content of the list def PrintList(self): temp = self.head if(temp != None): print("The list contains:", end=" ") while (True): print(temp.data, end=" ") temp = temp.next if(temp == self.head): break print() else: print("The list is empty.") # test the code MyList = LinkedList() #Add three elements at the end of the list. MyList.push_back(10) MyList.push_back(20) MyList.push_back(30) MyList.push_back(40) MyList.PrintList() #Delete the first node MyList.pop_front() MyList.PrintList()

The above code will give the following output:

The list contains: 10 20 30 40 The list contains: 20 30 40