Numpy import fails when embedding python in c

Question

I'm trying to embed a python program to c++ code. the problem I have is to use python script that contain an numpy import. for example, if i use the following c++ code

#include <Python.h>
int main(int argc,char *argv[])
{
double 
    x=2.,
    xp=4.,
    dt=6.,
    y=8,
    yp=1,
    dz=6;
Py_Initialize();

PyObject* myModuleString = PyString_FromString((char*)"log");
PyObject* myModule = PyImport_Import(myModuleString);


PyObject* myFunction = PyObject_GetAttrString(myModule,(char*)"derive");
PyObject* args = PyTuple_Pack(  6,
PyFloat_FromDouble(x),
PyFloat_FromDouble(xp),
PyFloat_FromDouble(dt),
PyFloat_FromDouble(y),
PyFloat_FromDouble(yp),
PyFloat_FromDouble(dz));

PyObject* myResult = PyObject_CallObject(myFunction, args);

PyObject *ts= PyTuple_GetItem(myResult,0);
PyObject *zs= PyTuple_GetItem(myResult,1);
double result_t = PyFloat_AsDouble(ts);
double result_z = PyFloat_AsDouble(zs);
printf("%3f \n %f \n", result_t,result_z);

Py_Finalize();

system("pause");

return 0;
}

with the following log.py script which contain the function derive

def derive(x,xp,dt,y,yp,dz):
return log(abs(x - xp)/dt),exp((y-yp)/dz)

it runs correctly, but if the log.py contain from numpy import array, it fails

from numpy import array
def derive(x,xp,dt,y,yp,dz):
return log(abs(x - xp)/dt),exp((y-yp)/dz)

Answer 1

I think you're linking statically but not retaining all of the symbols, which is required to load dynamic extension modules (i.e. -Xlinker -export-dynamic). See Linking Requirements, which recommends that you query the correct options from distutils.sysconfig.get_config_var('LINKFORSHARED').

BTW, the variadic function Py_BuildValue is a more convenient way to create args.