nested lists as arrays

[bruno modulix]

benjamin.cordes at blawrc.de wrote:
> Hi,
> 
> why can't I do this:
> 
>         dummy = self.elements[toy][tox]
> 
>         self.elements[toy][tox] = self.elements[fromy][fromx]
>         self.elements[fromy][fromx] = dummy
> 
> after initialising my nested list like this:
> 
>        self.elements = [[0 for column in range(dim)] for row in
> range(dim) ]
> 

Sorry, I'm not psychic enough to guess what is exactly your problem:
- what do you mean "can't do" ?  You have a traceback ? please post it. 
You have unexpected results ? please describe.
- what are self, dim, toy, tox, fromy, fromx ?
- is all that code in the same method ?
- etc etc

So please post more informations if you expect us to help you.


Note that the following code is correct:
 >>> l = [[0 for i in range(3)] for y in range(3)]
 >>> l
[[0, 0, 0], [0, 0, 0], [0, 0, 0]]
 >>> l[0][0] = 1
 >>> l
[[1, 0, 0], [0, 0, 0], [0, 0, 0]]
 >>> l[0][0], l[0][1] = l[0][1], l[0][0]
 >>> l
[[0, 1, 0], [0, 0, 0], [0, 0, 0]]
 >>>

So I guess that your problem has nothing to do with nested lists.

(Also note BTW that, thanks to the magic of multiple assignement, you 
don't need the dummy stuff. The pythonic idiom for swapping 2 bindings is
a, b = b, a)



-- 
bruno desthuilliers
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for 
p in 'onurb at xiludom.gro'.split('@')])"