[Python] Python - Linked List - Append

I'm trying to learn Linked Lists in python I've been given Linked List class and asked to create append method.

Here is the code provided.

class Node:
def __init__(self, item, next):
self.item = item
self.next = next

class LinkedList:
def __init__(self):
self.head = None

def add(self, item):
self.head = Node(item, self.head)

def remove(self):
if self.is_empty():
return None
else:
item = self.head.item
self.head = self.head.next
return item

def is_empty(self):
return self.head == None

def __str__(self):
tmp_str = ""
ptr = self.head
while ptr != None:
tmp_str += ptr.item + " "
ptr = ptr.next

return tmp_str


Here is my append method but there is something wrong with it. I know if the Linked list is empty I have to create one, problem starts when there's elements inside.

def append(self, item):
ptr = self.head
if ptr:
while ptr != None:
ptr = ptr.next
ptr = Node(item, ptr)
else:
self.head = Node(item, self.head)


Anyone can tell me what did I do wrong please? Any help is much appreciated.

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