Python - LinkedList confusion

class Node:    def __init__(self, data=None, next=None):        self.data = data        self.next = nextclass LinkedList:    def __init__(self):        self.head = None        def insert_at_end(self,data):   >>> this function is working        print('self.head: ', self.head)        if self.head is None:            self.head = Node(data, None)            return        itr = self.head        while itr.next != None:            itr = itr.next        itr.next = Node(data, None)

def insert_at_end(self,data):   >>> this function is NOT working    n = self.head    node = Node(data, None)    if n is None:        n = node        return    while n.next != None:        n = n.next    n.next = node

When I add a node at end, the function which is not working gives me an empty list but the function which is working gives me a list. I think I am missing a basic point but unable to understand. I am new to Python and learning DSA.

if __name__ == '__main__':    ll = LinkedList()    ll.insert_at_end(100)    ll.insert_at_end(101)    ll.print_ll()

The working function gave me 100-->101-->The non working function gave me empty linked list.

Below is the print function which I used in both cases.

    def print_ll(self):        if self.head == None:            print("Empty Linked List")            return        n = self.head        strll = ''        while n != None:            strll += str(n.data) +'-->'            print("linkedlist: ", strll)            n = n.next