How to retrieve the first added node when a LinkedList is created?

Question

I have created a linkedlist in Python using below classes:

class: Node

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

class LinkedList:

class LinkedList:
    def __init__(self):
        self.head = None
    def insert_at_beginning(self, data):
        temp = Node(data)
        if self.head is None:
            self.head = temp
        else:
            temp.next = self.head
            self.head = temp

    def insert_at_end(self, data):
        temp = Node(data)
        if self.head is None:
            self.head = temp
        else:
            curr = self.head
            while curr.next is not None:
                curr = curr.next
            curr.next = temp

    def insert_at_position(self, pos, data):
        temp = Node(data)
        if self.head is None:
            self.head = temp
        else:
            curr = self.head
            i = 1
            while i < pos:
                curr = curr.next
                i += 1
            temp.next = curr.next
            curr.next = temp

    def traverse_list(self):
        if self.head is None:
            print('List is empty')
        else:
            curr = self.head
            while curr.next is not None:
                print(curr.data)
                curr = curr.next

Below is the order I am calling the insertion methods.

ll = LinkedList()
ll.head = Node(1)
ll.insert_at_beginning(data=10)
ll.insert_at_beginning(data=11)
ll.traverse()

The elements printed in the output are: 11 & 10 which are the ones I inserted but I don't see the value 1 which is a node I added in the beginning. Is there any logic I missed here that is making the first value skip or not being considered ?

Answer 1

Your problem comes from while curr.next is not None: in traverse_list(). Assuming you're pointing your last node, its next node is obviously None. Therefore, it will stop the loop before printing the last node's data.

You can try this:

def traverse_list(self):
    if self.head is None:
        print('List is empty')
    else:
        curr = self.head
        while curr is not None:
            print(curr.data)
            curr = curr.next