execute_py.c

#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>

// -----------------------------------------------
// The function to run Python
// -----------------------------------------------

#define AS_STRING(X) AS_STRING2(X)
#define AS_STRING2(X) #X

// loads the function F from the shared lib
#define LOAD(F, R, ...)                                                                                                \
 R (*F)(__VA_ARGS__);                                                                                                  \
 *(void**)(&F) = dlsym(libpython_handle, AS_STRING(F));                                                                \
 if ((error = dlerror()) != NULL) {                                                                                    \
  fprintf(stderr, "%s\n", error);                                                                                      \
  return 1;                                                                                                            \
 }

static void* libpython_handle = NULL;

//---------------------------------

int init_python_interpreter(const char* python_so) {
 char* error;
 libpython_handle = dlopen(python_so, RTLD_GLOBAL | RTLD_LAZY);
 if (!libpython_handle) {
  fprintf(stderr, "Can not find Python !\n%s\n", dlerror());
  return 1;
 }
 dlerror();                   // Clear any existing error
 LOAD(Py_Initialize, void, ); // loads the functions that we will need
 (*Py_Initialize)();          // initialize the interpreter
 return 0;
}

//---------------------------------

int init_python_interpreter_from_env(const char* env_var) {
 char *python_so = getenv(env_var);
 if (!python_so) {
  fprintf(stderr, "Can not find the environment variable %s\n", env_var);
  return 1;
 }
 return init_python_interpreter(python_so);
}

//---------------------------------

int execute_python_file(const char* filename) {
 char* error;
 if (!libpython_handle) {
  fprintf(stderr, "Python is not initialized. You forget to call init_python_interpreter !\n");
  return 1;
 }

 // check Python is running
 LOAD(Py_IsInitialized, int, );
 if (!(*Py_IsInitialized)()) {
  fprintf(stderr, "Python Interpreter failed to initialize");
  return 1;
 }

 // Open the script file, report error, and run it in the interpreter
 FILE* file = fopen(filename, "r");
 if (!file) {
  fprintf(stderr, "file %s not found \n", filename);
  return 1;
 }
 // LOAD(PyRun_SimpleString, int, const char *);
 LOAD(PyRun_SimpleFile, int, FILE*, const char*);
 (*PyRun_SimpleFile)(file, filename);

 return 0;
}

//---------------------------------

int close_python_interpreter() {
 char* error;

 // close the interpreter
 LOAD(Py_Finalize, void, );
 (*Py_Finalize)();

 // close the shared lib
 dlclose(libpython_handle);

 return 0;
}