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
[code=python]
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_e lement[1] != 0):
print current_element[0]
current_element = current_element[1]
[/code]
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.

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

[kudos]

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

[pbmods]

Heya, kudos.

Please use CODE tags when posting source code:

[CODE=pytho n]
Python code goes here.
[/CODE]

[bartonc]

Heya, kudos.

Please use CODE tags when posting source code:

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

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]

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

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..ehehehehe he

[latte]

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..ehehehehe he

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

[Sui Generis22]

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
[code=python]
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_e lement[1] != 0):
print current_element[0]
current_element = current_element[1]
[/code]
Hope that made sense
-k

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?