How to print the object returned by PyRun_String?

Question

I would like to know how to use the return of Pyrun_String.

I already tried to use PyUnicode_DATA and PyObject_Str.

if (!(pstr = PyRun_String("a = 1", Py_single_input, pGlobal, pdict)))
    exit(printf("Error while running string\n"));


// I tried this

PyObject *pstr = PyObject_Str(pstr);

void* test = PyUnicode_DATA(pstr);
printf("%s\n", (char*)test);


// or this

if (!PyArg_Parse(pstr, "s", &cstr))
    exit(printf("Bad result type\n"));
printf("%s\n", cstr);

Answer 1

You can use PyObject_Repr() to get a string representation of the object (like Python's repr()) and then pass it to PyUnicode_AsUTF8() to get an UTF-8 encoded C string. Don't forget to check with PyUnicode_Check() first.

Working example:

#include <stdio.h>
#include <Python.h>

int main(int argc, char **argv) {
        if (argc != 2) {
                fprintf(stderr, "Usage: %s PYTHON_CODE\n", argv[0]);
                return 1;
        }

        Py_Initialize();
        PyObject *dict = PyDict_New();
        PyObject *pstr;

        if (!(pstr = PyRun_String(argv[1], Py_single_input, dict, dict))) {
                fputs("PyRun_String failed\n", stderr);
                return 1;
        }

        PyObject *rep = PyObject_Repr(pstr);

        if (!PyUnicode_Check(rep)) {
                fputs("repr is not unicode (this should not happen!)\n", stderr);
                return 1;
        }

        const char *str_rep = PyUnicode_AsUTF8(rep);
        puts(str_rep);
}

Example output:

$ ./x 'a = 1'
None
$ ./x '(1,2,3)'
(1, 2, 3)
None
$ ./x 'x = {"a": 1}; x; x["a"]'
{'a': 1}
1
None

You always end up with an additional None because that's the "return value" of the whole script.