Importing tensorflow when embedding python in c++ returns null

Question

I\'ve a question regarding embedding python into a C++ application. The setup is as follows: I have a large C++ application which generates some data (renders images in real

Answer 1

I've resolved the issue. I needed to set argc and argv with PySys_SetArgv. I've uncovered this using PyErr_Occurred() and PyErr_Print() right after the failed import to see the problem.

Answer 2

ref: https://docs.python.org/3.5/extending/embedding.html

main.cpp

#include <Python.h>
#include <iostream>
#include <QString>
#include <QDir>
#include <cstring>

using namespace std;

int main(int argc, char *argv[])
{
    PyObject *pName, *pModule, *pDict, *pFunc;
    PyObject *pArgs, *pValue;
    int i;

    if (argc < 3) {
        fprintf(stderr,"Usage: call pythonfile funcname [args]\n");
        return 1;
    }

    Py_SetProgramName((wchar_t*)L"test");

    Py_Initialize();

    PySys_SetArgv(argc, (wchar_t**)argv);
    PyRun_SimpleString("import tensorflow as tf\n"
                       "print(tf.__version__)\n");

    PyRun_SimpleString("import cv2\n"
                       "print(cv2.__version__)\n");

    QString qs = QDir::currentPath();
    std::wstring ws = qs.toStdWString();
    PySys_SetPath(ws.data());
    pName = PyUnicode_DecodeFSDefault(argv[1]);
    /* Error checking of pName left out */

    pModule = PyImport_Import(pName);
    Py_DECREF(pName);

    if (pModule != NULL) {
        pFunc = PyObject_GetAttrString(pModule, argv[2]);
        /* pFunc is a new reference */

        if (pFunc && PyCallable_Check(pFunc)) {
            pArgs = PyTuple_New(argc - 3);
            for (i = 0; i < argc - 3; ++i) {
                pValue = PyLong_FromLong(atoi(argv[i + 3]));
                if (!pValue) {
                    Py_DECREF(pArgs);
                    Py_DECREF(pModule);
                    fprintf(stderr, "Cannot convert argument\n");
                    return 1;
                }
                /* pValue reference stolen here: */
                PyTuple_SetItem(pArgs, i, pValue);
            }
            pValue = PyObject_CallObject(pFunc, pArgs);
            Py_DECREF(pArgs);
            if (pValue != NULL) {
                printf("Result of call: %ld\n", PyLong_AsLong(pValue));
                Py_DECREF(pValue);
            }
            else {
                Py_DECREF(pFunc);
                Py_DECREF(pModule);
                PyErr_Print();
                fprintf(stderr,"Call failed\n");
                return 1;
            }
        }
        else {
            if (PyErr_Occurred())
                PyErr_Print();
            fprintf(stderr, "Cannot find function \"%s\"\n", argv[2]);
        }
        Py_XDECREF(pFunc);
        Py_DECREF(pModule);
    }
    else {
        PyErr_Print();
        fprintf(stderr, "Failed to load \"%s\"\n", argv[1]);
        return 1;
    }
    Py_Finalize();
    return 0;
}

multiply.py

import tensorflow as tf
import cv2

def multiply(a,b):
    print(tf.__version__) 
    print(cv2.__version__) 
    print("Will compute", a, "times", b)
    c = 0
    for i in range(0, a):
        c = c + b
    return c