Re: [ctypes-users] passing multidimensional array to c function

[Diez B. R. <de...@we...>]

On Monday 09 June 2008 14:11:42 Mark Irvine wrote:
> Hello,
>
> I'm trying to send a multidimensional array from python to a c function
> using ctypes.
> I found this post here, which helped me get this far:
> http://sourceforge.net/mailarchive/message.php?msg_id=ll8n9yix.fsf%40python
>.net
>
>
> I have this c code:
>
> int getFromMultiArray(int (*list)[3]){
>     int result;
>     int i,j,val;
>
>     for(i=0;i<3;i++){
>         for(j=0;j<3;j++){
>             val = list[i][j];
>             printf("i %d, j %d, val %d\n",i,j,val);
>         }
>
>     }
>     result = list[1][1];
>     return result;
> }
>
>
> I run it with this c code and it returns results as expected:
> int main(void){
>
>     int list2[3][3] = {
>             {1,2,3},
>             {4,5,6},
>             {7,8,9}};
>
>
>     int result = getFromMultiArray(list2);
>     printf("result %d \n",result);
>
>     return 0;
> }
>
> When I run it, I get:
> i 0, j 0, val 1
> i 0, j 1, val 2
> i 0, j 2, val 3
> i 1, j 0, val 4
> i 1, j 1, val 5
> i 1, j 2, val 6
> i 2, j 0, val 7
> i 2, j 1, val 8
> i 2, j 2, val 9
> result 5
>
> In this case, it returns element [1][1] which is 5, so I think this is
> working just as i expect it to.
>
>
> Now I'm trying to do the same from python with ctypes.
> here's what I've done:
>
>
> from ctypes import *
> cdll.LoadLibrary('./_pointers.so')
>
> p = CDLL('./_pointers.so')
>
> threeInts_type = ARRAY( POINTER(c_int), 3)
> l1 = c_int * 3
> l1 = l1(1,2,3)
> l2 = c_int * 3
> l2 = l2(1,2,3)
> l3 = c_int * 3
> l3 = l3(1,2,3)
>
> print "l1[0]: ",l1[0]
>
> threeIntArray = threeInts_type(l1,l2,l3)

Shouldn't this be

threeIntArray = threeInts_type(pointer(l1), pointer(l2), pointer(l3))

Diez