Link List in Python

[sri2097]

Hi all, I have written a Link list implementation in Python (Although
it's not needed with Lists and Dictionaries present. I tried it just
for the kicks !). Anyway here is the code -

# Creating a class comprising of node in Link List.
class linklist:
def __init__(self, data=None,link=None):
self.data = data
self.link = link

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

def printing(node):
print "-"*80
print ("[data][link] ---> [data][link] and so on till the end")
print "-"*80
while 1:
if node.link:
print node.data, node.link,"--->",
node = node.link
else:
# Printing the last node and exiting.
print node.data, node.link
print ("All nodes printed")
break

def assigning():
global node1, node2, node3, node4
node1 = linklist([raw_input("Enter name: "), raw_input("Enter
address: ")])
node2 = linklist([raw_input("Enter name: "), raw_input("Enter
address: ")])
node3 = linklist([raw_input("Enter name: "), raw_input("Enter
address: ")])
node4 = linklist([raw_input("Enter name: "), raw_input("Enter
address: ")])
# Checking to see if all the node.data are getting populated.
print node1
print node2
print node3
print node4
print
linking()

def linking():
node1.link = node2
node2.link = node3
node3.link = node4
# Passing the node1 to the print function so that it prints the
rest of the nodes using the links.
printing(node1)

if __name__ == "__main__":
assigning()


Doubt -
Now, Here I needed only 4 nodes. But what if I need more nodes. Is
there any way to create the number of nodes at runtime. Since I plan to
'import' this module later. I wouldn't know how many nodes I need even
before executing it. So, my doubt is - Is there any way to create 'n'
number of object (here nodes) at runtime ?

Any general criticisms about the code are also welcome...

 

[Mike Meyer]

Hi all, I have written a Link list implementation in Python (Although
it's not needed with Lists and Dictionaries present. I tried it just
for the kicks !). Anyway here is the code -

Generally very nice.

# Creating a class comprising of node in Link List.
class linklist:
def __init__(self, data=None,link=None):
self.data = data
self.link = link

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

def printing(node):
print "-"*80
print ("[data][link] ---> [data][link] and so on till the end")
print "-"*80
while 1:
if node.link:
print node.data, node.link,"--->",
node = node.link
else:
# Printing the last node and exiting.
print node.data, node.link
print ("All nodes printed")
break
Doubt -
Now, Here I needed only 4 nodes. But what if I need more nodes. Is
there any way to create the number of nodes at runtime. Since I plan to
'import' this module later. I wouldn't know how many nodes I need even
before executing it. So, my doubt is - Is there any way to create 'n'
number of object (here nodes) at runtime ?

Sure:

node = None
for i in range(n):
node = linklist(i, node)

# Node now points to a linked list of n nodes, counting down as you traverse
# the list.

Any general criticisms about the code are also welcome...

Well, your __str__ on linklist makes printing node.data, node.link
equivalent to printing node.data, node.link.data, which is
confusing. Maybe you want to make the __str__ method different?

Also, the while loop in printing can be shortened a bit. The canonical
loop scanner looks like:

while node:
process(node)
node = node.link

You have a slightly different process for the last node, which
requires a conditional in the loop. By re-arranging things so the
difference happens on the first node, you process the first node
outside the loop, and drop the conditional in the loop:

def printing2(node):
print node.data, node.link,
node = node.link
while node:
print "-->", node.data, node.link,
node = node.link
print "\nAll nodes printed"

Ok, part of the difference was printing the trailing newline. I moved
that to the final print statement to make it work right.

<mike