newbie question convert C to python

[Adam DePrince]

On Tue, 2005-02-15 at 11:03, Steven Bethard wrote:
> Paul Rubin wrote:
> > doodle4 at gmail.com writes:
> > 
> >>How do i handle this piece of code in python:
> >>
> >># define vZero 15
> >># define vOne  20
> >>
> >>unsigned int vTable[Zero][One]
> >>
> >>if(vGroup[vZero][vOne] == 0)
> >>    {
> >>         vGroup[vZero][vOne]--
> >>         .....
> >>         .....
> >>    }
> > 
> > Simplest might be with a dictionary:
> > 
> > vGroup = {}    # I assume you meant vGroup not vTable
> > if vGroup[(vZero, vOne)] == 0:
> >    vGroup[(vZero, vOne)] -= 1
> >    .....
> >    .....
> 
> Or, if you like, the parentheses are unnecessary:
> 
> vGroup = {}
> if vGroup[vZero, vOne] == 0:
>     vGroup[vZero, vOne] -= 1
>     .....
> 
> This (or the semantically identical version with parentheses) is 
> definitely the best approach if you expect to have a lot of empty spots 
> in your table.
> 
> STeVe

One of the problems I see is the access of uninitialized values.  In C,
you *can* read these and it isn't a bad idea if you used memset, calloc
or friends.  If I know for sure this will be sparse, I'd reproduce it in
python like this.

vTable = []
for x in xrange( vZero ):
	vTable.append( [0,] * vOne )

Now you have a vZero x vOne "array" of zeros.  Treat it as you would
such a creature in C ... 

vTable[0][0] = 1
or whatever you want to do. 

I've seen this question before.  Lot in the archives for the subject "2D
array" from Dec 7th 2004 - Dec 10th 2004.

Steven and I recommended roughly opposite solutions at the time :-)

Adam DePrince