Two-dimensional arrays

[Anton Muhin]

Peter Slizik wrote:
> 
>   Hi pythoners,
> 
> I'm working on a problem in which I have to use 2-dimensional array.
> I'm sorry, but I feel I should describe it precisely, so the question 
> will be at the end of this mail.
> 
> I created the 2-dim array using
> 
>  >>> dim = 5
>  >>> array = [[0]*dim]*dim
> 
> Here's how it looks like (using PrettyPrint):
> 
>  >>> pprint.pprint(array)
> [[0, 0, 0, 0, 0],
>  [0, 0, 0, 0, 0],
>  [0, 0, 0, 0, 0],
>  [0, 0, 0, 0, 0],
>  [0, 0, 0, 0, 0]]
> 
> Then I tried to change some elements:
> 
>  >>> array[1][2] = 1
> 
> The result looks quite strange:
> 
>  >>> pprint.pprint(array)
> [[0, 0, 1, 0, 0],
>  [0, 0, 1, 0, 0],
>  [0, 0, 1, 0, 0],
>  [0, 0, 1, 0, 0],
>  [0, 0, 1, 0, 0]]
> 
> After a while of fooling around, I realised the problems is in 
> references.  The 2-dim array doesn't consist of five 1-dim arrays, but 
> of five references to the same array.
> 
> How can I overcome this problem? Or should I use some other approach to 
> solve this 2-dim array problem - so trivial in C, but 'unsolvable' in 
> Python?
> 
> Thanx in advance
> 
> Peter
> 

And take look at Numeric module.

hth,
anton.