How to implement linked list in Python??

[akadri1010]

I am new to Python programming..

Can anyone help me to write a simple Python program that creates a singly linked list and then prints the entries in it??
I know how to do in C?? But Python does not support pointers, so how to get around with this issue??

[kudos]

Hi
actually, python variables do 'points' to things, so in a sense python does support pointers. Here is an example program, that fills a list with numbers 1 to 5. Each
element in the list looks the following way: (value, pointer_to_next_element). Then it prints the content of the list

list = []
list.append([1,0])
current_element = list[0]
 
# build a linked list 1,2,3,4,5
 
for i in range(5):
 list.append([i+2,0])
 current_element[1] = list[i+1]
 current_element = list[i+1]
 
# traverse the list
# and print it to screen.
 
current_element = list[0]
while(current_element[1] != 0):
 print current_element[0]
 current_element = current_element[1]
 

Hope that made sense
-k

I am new to Python programming..

Can anyone help me to write a simple Python program that creates a singly linked list and then prints the entries in it??
I know how to do in C?? But Python does not support pointers, so how to get around with this issue??

[mwillis]

It isn't necessary to implement a linked list, since Python already has a build-in list data structure.

myList = []
myList.append("this")
myList.append("is")
myList.append("the")
myList.append("list")
for item in myList:
    print item
 

[kudos]

well...but you wouldn't have a linked list :)

[pbmods]

Heya, kudos.

Please use CODE tags when posting source code:

[CODE=python]
Python code goes here.
[/CODE]

[bartonc]

Heya, kudos.

Please use CODE tags when posting source code:

Python code goes here.
 

Surely, you are not admonishing one of the Python Forum's experts.
You must mean mwillis.?

[MojaveKid]

maybe something like this....

class Node:
    def __init__(self,value):
        self.data = value
        self.next = 0
 
class List:
    def __init__(self):
        self.firstNode = Node(0)
 
    def __ShowNodeData(self,aNode):
        if aNode.next != 0:
           print aNode.data
           self.__ShowNodeData(aNode.next)
 
    def Dump(self):
        self.__ShowNodeData(self.firstNode)
 
    def InsertAfter(self,aNode,aNewNode):
        aNewNode.next = aNode.next
        aNode.next = aNewNode
 
    def InsertBeginning(self,aNewNode):
        aNewNode.next = self.firstNode
        self.firstNode = aNewNode    
 
nodeA = Node("A")
nodeB = Node("B")
nodeC = Node("C")
nodeD = Node("D")
 
aList = List()
 
aList.InsertBeginning(nodeB)
aList.InsertAfter(nodeB,nodeD)
aList.InsertAfter(nodeD,nodeC)
aList.InsertAfter(nodeC,nodeA)
 
aList.Dump()
 
 

B
D
C
A

[latte]

@MojaveKid
Hi MojaveKid - this is good! Thanks for doing it!
I'm doing a public domain app at the moment which needs some code for a linked list, so I was wondering - may I use this in my app? ( You'll be credited as the author of it, no worries there... :) ).
Thanks again - bye for now -
- latte

[MojaveKid]

ahh...sure you can use it...
however, you must freely teach every python newbie who might also ask about implementing a linked list in Python...or no deal..ehehehehehe

[latte]

@MojaveKid
Heh.. sounds ok to me... :) Very many thanks - it's a very nice bit of code!
Bye for now -
- latte

[Sui Generis22]

@kudos
What is the purpose of the i+ in the [i+2]? I ran the code and removed the i+ why does it continuously print 2?