Python Embedded C++

Question

I have read few tutorial on python embedded c++. I had refer back to python object. https://docs.python.org/3/c-api/function.html

Python script:

import picamera 
from pylibdmtx.pylibdmtx import decode 
from time import sleep

import cv2
def test():
    camera = picamera.PiCamera()
    camera.start_preview()
    sleep(10)
    camera.stop_preview()

    camera.capture('image3.png')
    camera.close()

    data = decode(cv2.imread('/home/pi/image3.png'))
    return(data)

C++ Script

#include<Python.h>
#include<string>

int main(){
String data2;

Py_Initialize();

***Doing Some Stuff TO GET data from test() function in python script and store in variable data2

Py_Finalize();
}

I had use PyRun_SimpleString() to do before, it can work. But, it cannot pass the variable to C++. The result I want is it can store the string to the variable at C++. Example after C++ execute the python script, python function return "1234". And "1234" is store at C++ variable (data2)

Please, help me solve this problem. This is my first time python embedding c++, and have some guide please.

Again, if can please provide me solution on

***Doing Some Stuff TO GET data from test() function in python script and store in variable data2

Thanks very much.... Appreciate

Answer 1

If I understand correctly, you want your C++ code to call your Python test() function and get the string result of that function back so the C++ code can do something with it. If so, I think something like this would do the trick for you:

 std::string data;
 char fileName[] = "my_test_python_script.py";
 PyObject * moduleObj = PyImport_ImportModule(filename);
 if (moduleObj)
 {
    char functionName[] = "test";
    PyObject * functionObj = PyObject_GetAttrString(moduleObj, functionName);
    if (functionObj)
    {
       if (PyCallable_Check(functionObj))
       {
          PyObject * argsObject = PyTuple_New(0);
          if (argsObject)
          {
             PyObject * resultObject = PyEval_CallObject(functionObj, argsObject);
             if (resultObject)
             {
                if ((resultObject != Py_None)&&(PyString_Check(resultObject))) 
                {
                    data = PyString_AsString(resultObject);
                }
                Py_DECREF(resultObject);
             }
             else if (PyErr_Occurred()) PyErr_Print();

             Py_DECREF(argsObject);
          }
       }
       Py_DECREF(functionObj);
    }
    else PyErr_Clear();

    Py_DECREF(moduleObj);
 }

 std::cout << "The Python test function returned: " << data << std::endl;