sorry to be a proselytizer, but this would be trivial with Cython:
http://cython.org/
-Chris
On Tue, Dec 27, 2011 at 1:52 AM, Åke Kullenberg
<ake.kullenb...@gmail.com> wrote:
> After diving deeper in the docs I found the PyTuple_New alternative to
> building tuples instead of Py_BuildValue. It seems to work fine.
>
> But I am unsure of the INCREF/DECREF refcounting thing. Will I need any of
> those in the code below?
>
> Also, for generic c extensions, how can I check the refcounts of the
> variables to see they're ok?
>
> static PyObject *
> test(PyObject *self, PyObject *args)
> {
> PyArrayObject *py_in, *py_out, *py_out2;
> double *in, *out, *out2;
> int i, n, dims[2];
> if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &py_in))
> return NULL;
> if (NULL == py_in || not_doublevector(py_in)) return NULL;
> n = py_in->dimensions[0];
> dims[0] = n;
> dims[1] = 1;
> py_out = (PyArrayObject *) PyArray_FromDims(1, dims, NPY_DOUBLE);
> py_out2 = (PyArrayObject *) PyArray_FromDims(1, dims, NPY_DOUBLE);
> in = pyvector_to_Carrayptrs(py_in);
> out = pyvector_to_Carrayptrs(py_out);
> out2 = pyvector_to_Carrayptrs(py_out2);
> for (i=0; i<n; i++) {
> out[i] = in[i] * 2.0;
> out2[i] = in[i] * 3.0;
> }
> PyObject *tupleresult = PyTuple_New(2);
> PyTuple_SetItem(tupleresult, 0, PyArray_Return(py_out));
> PyTuple_SetItem(tupleresult, 1, PyArray_Return(py_out2));
> return tupleresult;
> }
>
> On Tue, Dec 27, 2011 at 5:11 PM, Åke Kullenberg <ake.kullenb...@gmail.com>
> wrote:
>>
>> I have put together a few c extensions following the documentation
>> on http://www.scipy.org/Cookbook/C_Extensions/NumPy_arrays. There is however
>> one thing that stumps me.
>>
>> To illustrate with a simple code snippet, the test function below
>> multiplies the input numpy double array by two. So far so good. But how
>> about if I want the function to return a tuple of two numpy arrays so I
>> could do 'a, b = myCLib.test(c)' from a Python script? It's straight forward
>> to convert C data structures to Python objects with Py_BuildValue, but how
>> can I do this for numpy arrays instead?
>>
>> static PyObject *
>> test(PyObject *self, PyObject *args)
>> {
>> PyArrayObject *py_in, *py_out;
>> double *in, *out;
>> int i, n, dims[2];
>> if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &py_in))
>> return NULL;
>> if (NULL == py_in || not_doublevector(py_in)) return NULL;
>> n = py_in->dimensions[0];
>> dims[0] = n;
>> dims[1] = 1;
>> py_out = (PyArrayObject *) PyArray_FromDims(1, dims, NPY_DOUBLE);
>> in = pyvector_to_Carrayptrs(py_in);
>> out = pyvector_to_Carrayptrs(py_out);
>> for (i=0; i<n; i++) {
>> out[i] = in[i] * 2.0;
>> }
>> return PyArray_Return(py_out);
>> }
>
>
>
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>
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