Python C API

가장 간단하게 Python을 C에 embed 시키는 방법은 Very High Level interface를 사용 하는 것이다. VHL interface는 어플리케이션과 직접적인 상관 없이 Python script를 실행하기 위한 것이다.

관련 문서

Python/C API Reference Manual

우선 Python C API 관련 Include, Library 디렉토리를 프로젝트에 추가한다.

파이썬 공식 홈페이지에서 다운 받은 파이썬 인스톨러 패키지를 설치 했다면 Solution Configurations를 Release로 설정 한다. Debug 모드로 build 할 경우 pythonXX_d.lib를 찾을 수 없다는 에러가 발생한다. pythonXX_d.lib 파일을 생성하려면 파이썬 소스를 받아서 직접 컴파일해야 한다.

예제:

#pragma comment(lib, "python36.lib")
#include <Python.h>
 
int main(int argc, char *argv[])
{
    wchar_t *program = Py_DecodeLocale(argv[0], NULL);
    // Decode a byte string from the locale encoding with the surrogateescape error handler:
    // undecodable bytes are decoded as characters in range U+DC80..U+DCFF. If a byte sequence
    // can be decoded as a surrogate character, escape the bytes using the surrogateescape error
    // handler instead of decoding them.
    // Return a pointer to a newly allocated wide character string, use PyMem_RawFree() to free
    // the memory. If size is not NULL, write the number of wide characters excluding the null
    // character into *size
    if (program == NULL) {
        fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
        exit(1);
    }
    Py_SetProgramName(program);  /* optional but recommended */
    // This function should be called before Py_Initialize() is called for the first time, if it
    // is called at all.It tells the interpreter the value of the argv[0] argument to the main()
    // function of the program(converted to wide characters).This is used by Py_GetPath() and some
    // other functions below to find the Python run - time libraries relative to the interpreter
    // executable.
 
    Py_Initialize();
    // Initialize the Python interpreter. In an application embedding Python, this should be called
    // before using any other Python/C API functions
    if (Py_IsInitialized())
    // Return true (nonzero) when the Python interpreter has been initialized, false (zero) if not.
    // After Py_FinalizeEx() is called, this returns false until Py_Initialize() is called again.
    {
        PyRun_SimpleString("print('Hello Python')");
        // This is a simplified interface to PyRun_SimpleStringFlags(), leaving the PyCompilerFlags*
        // argument set to NULL.
        PyRun_SimpleString("from time import time, ctime\n"
            "print('Today is', ctime(time()))\n");
        //PyRun_SimpleString("from time import time, ctime\nprint('Today is', ctime(time()))\n");
 
        if (Py_FinalizeEx() < 0)
        // Undo all initializations made by Py_Initialize() and subsequent use of Python/C API
        // functions, and destroy all sub-interpreters that were created and not yet destroyed
        // since the last call to Py_Initialize().
        {
            exit(120);
        }
        PyMem_RawFree(program);
        // Frees the memory block pointed to by p, which must have been returned by a previous call
        // to PyMem_RawMalloc(), PyMem_RawRealloc() or PyMem_RawCalloc().
        // Otherwise, or if PyMem_RawFree(p) has been called before, undefined behavior occurs.
        // If p is NULL, no operation is performed.
    }
 
    return 0;
}