I tried to create a simple single-linked list as the following:

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


class linkedlist:
    def __init__(self):
        self.head = node()

    def append(self, data):
        curr = self.head
        new_node = node(data)
        while curr.next != None:
            curr = curr.next
        curr.next = new_node

    def total(self):
        curr = self.head
        total = 0
        while curr.next != None:
            curr = curr.next
            total += 1
        return total

    def display(self):
    # added total here as well
        curr = self.head
        em = []
        total = 0
        while curr.next != None:
            curr = curr.next
            em.append(curr.data)
            total += 1
        print(f"LinkedList: {em} n Total: {self.total()}  ")

    def look(self, index):
        if index >= self.total():
            print("ERROR: Index error" )
        curr_index = self.head
        idx = 0
        while True:
            curr_index = curr_index.next
            if idx == index:
                print(curr_index.data)
            idx += 1

Whenever I am calling the look() function, I am getting the following error:

curr_index = curr_index.next
             ^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'next'

What could this mean?

As far as I know, the curr_index is using the self.head, which is inturn using node(). The node() have does have the next attribute.

This error isn’t there when I call the other functions in the class. Moreover, the other functions — except the look() function — returns their respective values error-free.

Where is my code going wrong?