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I am trying to call a python function from a C++ application. The tutorial I am using is here (just the documentation): https://docs.python.org/3/extending/embedding.html

The issue is that I am getting a: ModuleNotFoundError: no module named 'multiply'

This is the code I am using:

C++ file (test.cpp):

#include <Python.h>
#include <stdio.h>
#include <iostream>


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

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

    Py_Initialize();

    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]);
    }
    if (Py_FinalizeEx() < 0) {
        return 120;
    }
    return 0;
}

Python script (multiply.py):

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

And the Cmakefile:

cmake_minimum_required(VERSION 3.11)
project( EmbedMain )

set(CMAKE_CXX_STANDARD 11)

find_package(PythonLibs REQUIRED)
include_directories(${PYTHON_INCLUDE_DIRS})

add_executable( EmbedMain test.cpp )
target_link_libraries(EmbedMain ${PYTHON_LIBRARIES})

I would run it like: ./EmbedMain multiply multiply 2 3 For some reason it is giving me a ModuleNotFoundError when the program hits the if (pModule != NULL) I have no clue why this is happening and would appreciate any help.

EDIT:

I read the documentation for PyImport_Import() and it says that this function always uses absolute imports. How can I tell if my multiply.py is an absolute import?

Sed
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