Simple Example How To Call Python Function in C/C++

Question

i have already searched through google, and many refence, but i only see a complex example of coding, would you give me an example (In Simple Code) so i can understand. I've already code it, but it breaks everytime i run it Here's the code

#include <Python.h>
int main()
{
  PyObject *pName, *pModule, *pDict, *pFun, *pValue;
  // Initialize the Python Interpreter
  Py_Initialize();
 // Build the name object
 pName = PyString_FromString("C:\\Documents and Settings\\MASTER\\My Documents\\Visual Studio       2010\\Projects\\Python\\Test.py");
if(pName)printf("OK");

// Load the module object
pModule = PyImport_Import(pName);

// pDict is a borrowed reference 
pDict = PyModule_GetDict(pModule);

// pFunc is also a borrowed reference 
pFun = PyDict_GetItemString(pDict, "prinTname");

if (PyCallable_Check(pFun)) 
{
    PyObject_CallObject(pFun, NULL);
} else 
{
    PyErr_Print();
}

// Clean up
Py_DECREF(pModule);
Py_DECREF(pName);

Py_DECREF(pDict);
Py_DECREF(pFun);
// Finish the Python Interpreter
Py_Finalize();
getchar();
return 0;
}

and there are some messages First-chance exception at 0x1e00503b in Python.exe: 0xC0000005: Access violation reading location 0x00000004. Unhandled exception at 0x1e00503b in Python.exe: 0xC0000005: Access violation reading location 0x00000004. The program '[4548] Python.exe: Native' has exited with code 0 (0x0).

As for your problem, have you tried running you program in a debugger? Are you sure all function calls succeed? — Some programmer dude
– Some programmer dude, Commented Oct 28, 2012 at 13:41
I have already built it in VS 2010 and it built succeeded, i just want to call it in C/C++ this is the python code : def prinTname(): print "OK Fun" — Yoshua Joo Bin
– Yoshua Joo Bin, Commented Oct 28, 2012 at 13:45

Dennis · Accepted Answer · 2013-02-04 02:26:44Z

Here's some code from a question I asked. This should do what you want.

Args: argv[1] contains the path to your .py file argv[2] contains the name of the function you want to call

int wmain(int argc, wchar_t** argv)
{
    PyObject* py_imp_str;
    PyObject* py_imp_handle;
    PyObject* py_imp_dict; //borrowed
    PyObject* py_imp_load_source; //borrowed
    PyObject* py_dir; //stolen
    PyObject* py_lib_name; //stolen
    PyObject* py_args_tuple;
    PyObject* py_lib_mod;
    PyObject* py_func;
    PyObject* py_ret;

    Py_Initialize();

    //import our python script using the imp library (the normal import doesn't allow you to grab py files in random directories)
    py_dir = PyUnicode_FromWideChar(argv[1], wcslen(argv[1]));
    py_imp_str = PyString_FromString("imp");
    py_imp_handle = PyImport_Import(py_imp_str); //normal python import for imp
    py_imp_dict = PyModule_GetDict(py_imp_handle); //borrowed
    py_imp_load_source = PyDict_GetItemString(py_imp_dict, "load_source"); //borrowed
    py_lib_name = PyUnicode_FromWideChar(argv[2], wcslen(argv[2]));

    //setup args for imp.load_source
    py_args_tuple = PyTuple_New(2);
    PyTuple_SetItem(py_args_tuple, 0, py_lib_name); //stolen
    PyTuple_SetItem(py_args_tuple, 1, py_dir); //stolen

    //call imp.load_source
    py_lib_mod = PyObject_CallObject(py_imp_load_source, py_args_tuple);
    py_lib_mod_dict = PyModule_GetDict(py_lib_mod); //borrowed

    //get function object
    py_func = PyDict_GetItem(py_lib_mod_dict, py_lib_name);
    //call function object
    py_ret = PyObject_CallFunction(py_func, NULL);

    if (py_ret)
    {
        printf("PyObject_CallFunction from wmain was successful!\n");
        Py_DECREF(py_ret);
    }
    else
        printf("PyObject_CallFunction from wmain failed!\n");

    Py_DECREF(py_imp_str);
    Py_DECREF(py_imp_handle);
    Py_DECREF(py_args_tuple);
    Py_DECREF(py_lib_mod);

    Py_Finalize();

    fflush(stderr);
    fflush(stdout);
    return 0;
}

If you haven't found this already, the following link describes the C interface to Python. Very handy: http://docs.python.org/2/c-api/index.html

Community · Accepted Answer · 2017-05-23 12:34:01Z

0

You most likely have not installed python dev tools, i.e. python.h is never found. Locate python.h and look for compile errors and repost if there are some.

Edit: This is old info. Including should be as easy as adding the include directory to the include directories, see: How do I get Visual Express 2010 to find my python.h header file?

edited May 23, 2017 at 12:34

CommunityBot

11 silver badge

answered Oct 28, 2012 at 13:43

RParadox

6,9314 gold badges26 silver badges35 bronze badges

6 Comments

Yoshua Joo Bin Over a year ago

How to add Python File (*.py) into my C/C++ project in my VS2010 ? can you give me a simple example how to call python function in C/C++ ?

RParadox Over a year ago

You need python-dev first. If you just want to call Python from C see docs.python.org/release/2.4.2/ext/callingPython.html or codeproject.com/Articles/11805/Embedding-Python-in-C-C-Part-I

Yoshua Joo Bin Over a year ago

python-dev ? is it a tools/sdk ? where i can get it ?

RParadox Over a year ago

See my post ;) If you install python-dev python.h will be found (hopefully). Actually those windows links don't explain it. It has to be somewhere though.

RParadox Over a year ago

Sorry, this is old info. Python.h can now be found in the Python/include folder.

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