'Node' object has no attribute 'set_next'

Question

When I insert a new node I get AttributeError: 'Node' object has no attribute 'set_next'. I can't really understand why, because in my Node class I have a method set_next. And isn't that the one I'm calling?

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

        def get_data(self):
            return self.val

        def set_data(self, val):
            self.val = val

        def get_next(self):
            return self.next

        def set_next(self, next):
            self.next = next

class LinkedList(object):
    def __init__(self, head=None):
        self.head = head
        self.count = 0 

    def get_count(self):
        return self.count

    def insert(self, data):
        new_node = Node(data)
        new_node.set_next()
        self.head = new_node
        self.count += 1

The expected output is that the new node should be the new head node.

Answer 1

This will fix the AttributeError and the subsequent TypeError.

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

    # fixed indentation here
    def get_data(self):
        return self.val

    def set_data(self, val):
        self.val = val

    def get_next(self):
        return self.next

    def set_next(self, next):
        self.next = next

class LinkedList(object):
    def __init__(self, head=None):
        self.head = head
        self.count = 0 

    def get_count(self):
        return self.count

    def insert(self, data):
        new_node = Node(data)
        # fix logic here
        new_node.set_next(self.head)
        self.head = new_node
        self.count += 1

Testing

linked_list = LinkedList()
linked_list.insert('hello')
linked_list.insert('world')
print(linked_list.count)
print(linked_list.head.val)
print(linked_list.head.next.val)

outputs

2
world
hello

Note that, as you can see, this LinkedList inserts only at the front of the list, not the end.

---

Bonus

If you want to iterate over the list, use this method

def __iter__(self):
   node = self.head
   while node is not None:
       yield node.val
       node = node.next

Answer 2

I tried this and hope this helps you:

class Node(object):
    def __init__(self, val):
        self.val = val
        self.next = None
    def get_data(self):
        return self.val
    def set_data(self, val):
        self.val = val
    def get_next(self):
        return self.next
    def set_next(self, next):
        self.next = next

class LinkedList(object):
    def __init__(self, head=None):
        self.head = head
        self.count = 0 
    def get_count(self):
        return self.count
    def insert(self, data):
        new_node = Node(data)
        new_node.set_next(self.head)
        self.head = new_node
        self.count += 1
>>> itemList = LinkedList()
>>> itemList.insert(38)
>>> itemList.insert(40)
>>> itemList.get_count()
2

Answer 3

With your indentation as it stands,

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

        def get_data(self):
            return self.val

get_data and the following functions, including set_next are local to the __init__ method.

So, as the error says, the "Nodeclass does not have aset_next` method.

You need to pull them back:

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

    def get_data(self):
        return self.val

    #... and the rest

This will give your further problems, but fix your initial problem.

Next, you will see

File "linked.py", line 28, in insert
  new_node.set_next()
  TypeError: set_next() missing 1 required positional argument: 'next'

As was said in the comments, you need to pass this a value. I suspect you are trying to set next on the head or final node to this new_node.