Extending and Embedding

#include "Python.h"

static PyObject * spam_system(PyObject *self, PyObject *args)
{
         char *command;
         int sts;

         if (!PyArg_ParseTuple(args, "s", &command))
             return NULL;
         sts = system(command);
         return Py_BuildValue("i", sts);
}

 
>>> import spam
>>> status = spam.system("ls -l")

arglist = Py_BuildValue("(i)", arg);
result = PyEval_CallObject(pyfunction, arglist);

/* Example of embedding Python in another program */

#include "Python.h"

static char *argv0;

void initxyzzy(); /* Forward */

main(argc, argv)
	int argc;
	char **argv;
{
	/* Save a copy of argv0 */
	argv0 = argv[0];

	/* Initialize the Python interpreter.  Required. */
	Py_Initialize();

	/* Add a static module */
	initxyzzy();

	/* Define sys.argv.  It is up to the application if you
	   want this; you can also let it undefined (since the Python 
	   code is generally not a main program it has no business
	   touching sys.argv...) */
	PySys_SetArgv(argc, argv);

	/* Do some application specific code */
	printf("Hello, brave new world\n\n");

	/* Execute some Python statements (in module __main__) */
	PyRun_SimpleString("import sys\n");
	PyRun_SimpleString("print sys.builtin_module_names\n");
	PyRun_SimpleString("print sys.modules.keys()\n");
	PyRun_SimpleString("print sys.argv\n");

	/* Note that you can call any public function of the Python
	   interpreter here, e.g. call_object(). */

	/* Some more application specific code */
	printf("\nGoodbye, cruel world\n");

	/* Exit, cleaning up the interpreter */
	Py_Exit(0);
	/*NOTREACHED*/
}

/* This function is called by the interpreter to get its own name */
char *
getprogramname()
{
	return argv0;
}

/* A static module */

static PyObject *
xyzzy_foo(self, args)
	PyObject *self; /* Not used */
	PyObject *args;
{
	if (!PyArg_ParseTuple(args, ""))
		return NULL;
	return PyInt_FromLong(42L);
}

static PyMethodDef xyzzy_methods[] = {
	{"foo",		xyzzy_foo,	1},
	{NULL,		NULL}		/* sentinel */
};

void
initxyzzy()
{
	PyImport_AddModule("xyzzy");
	Py_InitModule("xyzzy", xyzzy_methods);
}