How do you properly load a python(3.0) function in c++

Question

I have only been able to find tutorials and links for python 2 not any for 3. A lot of functions have changed since 2 and the tutorials no longer work.

I was able to take this from a another Stackoverflow question and it seems to be the closest to working.

char *my_result = 0;
PyObject *module = 0;
PyObject *result = 0;
PyObject *module_dict = 0;
PyObject *func = 0;
PyObject *pArgs = 0;

module = PyImport_ImportModule("testPython");
if (module == 0)
{
    PyErr_Print();
    printf("Couldn't find python module");
}
module_dict = PyModule_GetDict(module); 
func = PyDict_GetItemString(module_dict, "helloWorld"); 

//result = PyObject_CallObject(func, NULL);
result = PyEval_CallObject(func, NULL);
my_result = PyBytes_AsString(result);
my_result = strdup(my_result);

But the my_result outputs 0000. And when using a breakpoint it says it cannot read the memory.

what isn't working? Are there error messages? Compile-time? runtime? — mgilson
– mgilson, Commented Mar 19, 2014 at 6:10
@mgilson I updated my question at the bottom. "But the my_result outputs 0000. And when using a breakpoint it says it cannot read the memory." — user3436172
– user3436172, Commented Mar 19, 2014 at 6:19
error handling 101: 1) always check the return value 2) if something unrecoverable happens, don't continue. — Karoly Horvath
– Karoly Horvath, Commented Mar 19, 2014 at 7:13

ohmu · Accepted Answer · 2014-03-19 19:20:12Z

1

Try this:

static float CallPythonFunc()
{
    PyObject *pName, *pModule, *pDict, *pFunc, *pValue, *pArgs;
    float ret;

    Py_Initialize();

    pName = PyBytes_FromString("py");

    pModule = PyImport_ImportModule("py");

    pDict = PyModule_GetDict(pModule);

    pFunc = PyDict_GetItemString(pDict, "add");


    if (PyCallable_Check(pFunc))
    {
        pArgs = PyTuple_New(2 /*number of arguments*/);

        // Argument 1
        pValue = PyFloat_FromDouble((double)5);
        PyTuple_SetItem(pArgs, 0, pValue);

        // Argument 2
        pValue = PyFloat_FromDouble((double)6);
        PyTuple_SetItem(pArgs, 1, pValue);

        pValue = PyObject_CallObject(pFunc, pArgs);

        ret = (float)PyFloat_AsDouble(pValue);

    }
    Py_Finalize();

    return ret;
}

edited Mar 19, 2014 at 19:20

ohmu

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answered Mar 19, 2014 at 16:46

bbdude95

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