The first operation that we need to perform is to append items to the list. This operation is sometimes called an insert operation. Here we get a chance to hide away the Node class. The user of our list class should really never have to interact with Node objects. These are purely for internal use.

The first shot at an append() method may look like this:

class SinglyLinkedList:
    # ...
    def append(self, data):
         # Encapsulate the data in a Node 
         node = Node(data)
         if self.tail == None:
             self.tail = node 
         else:
             current = self.tail 
             while current.next:
                 current = current.next 
             current.next = node

We encapsulate data in a node so that it has the next pointer attribute. From here, we check if there are any existing nodes in the list (that is, whether self.tail points to a Node or not). If there is None, we make the new node the first node of the list; otherwise, we find the insertion point by traversing the list to the last node, updating the next pointer of the last node to the new node.

Consider the following example code to append three nodes:

>>> words = SinglyLinkedList()
>>> words.append('egg')
>>> words.append('ham')
>>> words.append('spam')

List traversal will work as we discussed before. You will get the first element of the list from the list itself, and then traverse the list through the next pointer:

>>> current = words.tail
>>> while current:
        print(current.data)
        current = current.next