Singly Linked List, thesarfo

A singly linked list has only one pointer between two successive nodes, so it can only be traversed in a single direction — from the first node to the last, never the other way round.

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

n1 = Node('eggs')
n2 = Node('ham')
n3 = Node('spam')

n1.next = n2
n2.next = n3

To traverse the list:

current = n1
while current:
    print(current.data)
    current = current.next

Each iteration prints the current element, then advances current to the next one, until the end of the list is reached. Simple, but a raw node chain like this isn’t a good abstraction on its own.

Singly Linked List Class

A list is a separate concept from a node, so it gets its own class. Start with a constructor holding a reference to the first node — since the list starts empty, that reference starts as None:

class SinglyLinkedList:
    def __init__(self):
        self.tail = None