Re: A question about reference in Python.

Hi,

This is really really really pointless code and a really really pointless
exercise, but nonetheless, here is a very very basic and minimal
implementation of what you're expecting. This should almost
*never* be done in Python! Python is a superior dynamic programming
language, but it's NOT C!

Here goes:

jmills@atomant:~/tmp$ ./list.py
x[0]
0
x[1]
1
x[2]
2
x[3]
3
x[4]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "./list.py", line 36, in __getitem__
return node.value
AttributeError: 'NoneType' object has no attribute 'value'

jmills@atomant:~/tmp$

And the code:

#!/home/jmills/bin/python -i

class Node(object):

value = None
prev = None
next = None

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

class List(object):

data = None

def __init__(self, *seq):
if seq:
first = prev = node = None
for x in seq:
if not first:
first = Node(x)
prev = node = first
else:
node = Node(x, prev)
prev.next = node
prev = node

self.data = first

def __getitem__(self, x):
node = self.data
for i in xrange(x):
node = node.next
return node.value

x = List(0, 1, 2, 3)


Notes:

I have not implemented any error checking whatsoever.
I have not implemented any of your normal list
operations whatsoever (except 1). __getitem__.

Have fun,

cheers
James

On Mon, Dec 8, 2008 at 3:26 PM, Group <kermit.group@xxxxxxxxx> wrote:
Hello, I'm studying algorithom. For concentrating on the question itself, I
intend to use Python to implement the algorithoms.

Now, I want to write a Red-Black Tree, and a List structure. In C/C++, I can
use pointers to refer to children notes (or next notes). But, in Python,
how
can I do it? Except the sequence, I know not any way.

You'd better help me understan how can I transform the following C code into
Python:

/* a List */
struct {
int data;
int *next;
int *prev;
}

That's all. Thanks!
Kermit

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