I was just playing around in python trying to get a basic sort of linked list working. I was able to make a simple linked list using an article I read online that looks like this:

class node:
    def __init__(self, value = None, next = None):
        self.value = value
        self.next = next

def printList(node):
    print "[",
    while node:
        print node,
        node = node.next
    print "]"

def printBackward(list):
    if list == None:
        return
    head = list
    tail = list.next
    printBackward(tail)
    print head,

def removeSecond(list):
    if list == None:
        return
    first = list
    second = list.next
    #Make the first node refer to the third
    first.next = second.next
    # seperate the second node from the rest of the list
    second.next = None
    return second

That just allowed you to make a linked list and remove some elements or print it backwards, simple things like that.
EX:

>>> node1 = node(1)
>>> node2 = node(2)
>>> node3 = node(3)
>>> node1.next = node2
>>> node2.next = node3
>>> printList(node1)
[ 1 2 3 ]
>>>
>>> printBackward(node1)
3 2 1

The problem is that I start to get confused when trying to add elements to the start of the list. I tried to keep using the node class but then add in a linkedList class and an addFirst function, as well as a new function to print the list.

I came up with this:

class node:
    def __init__(self, value = None, next = None):
        self.value = value
        self.next = next

    def __str__(self):
        return str(self.value)

class linkedList:
    def __init__(self):
        self.length = 0
        self.head = None

def addFirst(list,value):
    first = node(value)
    if list.head != None:
        second = list.head
        first.next = second
    list.head == first
    list.length += 1

def printlst(list):
    print "[",
    cursor = list.head
    while cursor != None:
        print cursor.value
        cursor = cursor.next
    print "]"

I trid to run it by doing something like

>>>newList = linkedList()
>>> addFirst(newList,4)
>>> printlst(newList)
[]

Whenever I try that it always just returns me those brackets and I don't quite understand why. If someone could help me figure out a way to set up a linked list and add or remove elements from it without making a specific instance like the "removeSecond" above then I'd really appreciate it.

Also: I've looked into making everything a method and I was not able to figure out what to do, so I'd prefer if someone could explain it in a way that doesn't involve the add functions being methods. Of course you can still give a shot at explaining it to me if you want to.

Thanks for any help in advance.

I'm not sure I fully understand your questions, but the reason your addFirst does not work seems to be line 19:

Should be list.head = first instead of list.head == first

Comments
great!

I'm not sure I fully understand your questions, but the reason your addFirst does not work seems to be line 19:

Should be list.head = first instead of list.head == first

Wow, words can not express how stupid I feel right now... I had been having trouble figuring out why it wasn't working because it wasn't returning any runtime or syntax errors and I wasn't too confident in my abilities so I thought there was something wrong. Well thanks for your help anyway =D, guess I knew more than I thought

This question has already been answered. Start a new discussion instead.