Py_BuildValue - return large array

[Christian Tismer]

Howdy,

thanks for your good advice.
But I suggest to never leave the error checking
code, since that teaches sloppy style to newcomers.
Added error checking:

"Michael P. Reilly" wrote:
> 
> j vickroy <jvickroy at sec.noaa.gov> wrote:
> : Hello all,
> 
> : How should one return a (handle to?) "large" C-array to Python?
> 
> : It seems that Py_BuildValue ("[...]", ..., ...) is only usable for
> : "small" arrays where one can explicitly enumerate each element in the
> : array.
> 
> : Thanks for your time.
> 
> You probably don't want to use Py_BuildValue().  For one, if you have a
> large array, then you might have problems enumerating the values in the
> function call (as seperate arguments).
> 
> I would suggest creating a Python list object explicitly and populating
> it that way.  For example,
> 
> PyObject *Convert_Big_Array(long array[], int length)
>   { PyObject *pylist, *item;
>     int i;
>     pylist = PyList_New(length);
>     for (i=0; i<length; i++) {
>       item = PyInt_FromLong(array[i]);
>       PyList_SetItem(pylist, i, item);
>     }
>     return pylist;
>   }

Here the same routine, using an error check, plus
the (somewhat faster) PyList_SET_ITEM macro.

PyObject *Convert_Big_Array(long array[], int length)
  { PyObject *pylist, *item;
    int i;
    pylist = PyList_New(length);
    if (pylist != NULL) {
      for (i=0; i<length; i++) {
        item = PyInt_FromLong(array[i]);
        PyList_SET_ITEM(pylist, i, item);
      }
    }
    return pylist;
  }

ciao - chris

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