Python program to delete a new node from the beginning of the doubly linked list
#Represent a node of doubly linked list
class Node:
def __init__(self,data):
self.data = data;
self.previous = None;
self.next = None;
class DeleteStart:
#Represent the head and tail of the doubly linked list
def __init__(self):
self.head = None;
self.tail = None;
#addNode() will add a node to the list
def addNode(self, data):
#Create a new node
newNode = Node(data);
#If list is empty
if(self.head == None):
#Both head and tail will point to newNode
self.head = self.tail = newNode;
#head's previous will point to None
self.head.previous = None;
#tail's next will point to None, as it is the last node of the list
self.tail.next = None;
else:
#newNode will be added after tail such that tail's next will point to newNode
self.tail.next = newNode;
#newNode's previous will point to tail
newNode.previous = self.tail;
#newNode will become new tail
self.tail = newNode;
#As it is last node, tail's next will point to None
self.tail.next = None;
#deleteFromStart() will delete a node from the beginning of the list
def deleteFromStart(self):
#Checks whether list is empty
if(self.head == None):
return;
else:
#Checks whether the list contains only one element
if(self.head != self.tail):
#head will point to next node in the list
self.head = self.head.next;
#Previous node to current head will be made None
self.head.previous = None;
#If the list contains only one element
#then, it will remove the node, and now both head and tail will point to None
else:
self.head = self.tail = None;
#display() will print out the nodes of the list
def display(self):
#Node current will point to head
current = self.head;
if(self.head == None):
print("List is empty");
return;
while(current != None):
#Prints each node by incrementing pointer.
print(current.data),
current = current.next;
print();
dList = DeleteStart();
#Add nodes to the list
dList.addNode(1);
dList.addNode(2);
dList.addNode(3);
dList.addNode(4);
dList.addNode(5);
#Printing original list
print("Original List: ");
dList.display();
while(dList.head != None):
dList.deleteFromStart();
#Printing updated list
print("Updated List: ");
dList.display();
Output:
Original List:
1 2 3 4 5
Updated List:
2 3 4 5
Updated List:
3 4 5
Updated List:
4 5
Updated List:
5
Updated List:
List is empty
