无法append到python中的链表

Question

I'm trying to learn how to create linked lists. This is my first time doing this and the reason of code failure may be something basic I'm missing.

That being said, I am unable to figure out even after using vs code's debugger. It simply stops at the end of the append method when it is called the second time.

I am using recursion to traverse to the tail. Could that be a the problem?

class Node:

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


class LinkedList:

    def __init__(self):
        self.head = None

    def __repr__(self):

        if not self.head:
            return 'Linked list is empty'

        linked_list = self.head.data

        if self.head.next == None:
            return linked_list

        current = self.head

        while current.next != None:
            linked_list += '\n|\nV' + current.data

        return linked_list

    def append(self, value):

        if not self.head:
            self.head = Node(data=value)
            return

        tail = self.tail()

        tail.next = Node(data=value)

    def tail(self):

        tail = self._traverse_to_tail(self.head)

        while tail.next != None:
            tail = self._traverse_to_tail(tail)

        return tail

    def _traverse_to_tail(self, current_node, recursion_count=0):
        print(current_node.data)
        if recursion_count > 997:
            return current_node

        if current_node.next == None:
            return current_node

        current_node = current_node.next
        recursion_count += 1

        return self._traverse_to_tail(current_node, recursion_count)


if __name__ == '__main__':
    ll = LinkedList()

    ll.append('foo')
    ll.append('baz')

    print(ll)

Answer 1

The problem is you have an infinite loop in the __repr__() function, because you never increment current .

    def __repr__(self):

        if not self.head:
            return 'Linked list is empty'

        linked_list = self.head.data

        if self.head.next == None:
            return linked_list

        current = self.head

        while current.next != None:
            current = current.next
            linked_list += '\n|\nV' + current.data

        return linked_list