to a Python variable name. As a result, it’s probably more similar to the Python
import built-in function.
The PyRun_String call is the one that actually runs code here, though. It takes a code
string, a parser mode flag, and dictionary object pointers to serve as the global and local
namespaces for running the code string. The mode flag can be Py_eval_input to run an
expression or Py_file_input to run a statement; when running an expression, the result
of evaluating the expression is returned from this call (it comes back as a PyObject*
object pointer). The two namespace dictionary pointer arguments allow you to distin-
guish global and local scopes, but they are typically passed the same dictionary such
that code runs in a single namespace.
Example 20-26. PP4E\Integrate\Embed\Basics\embed-string.c
/ code-strings with results and namespaces /
#include <Python.h>
main() {
char cstr;
PyObject pstr, pmod, pdict;
printf("embed-string\n");
Py_Initialize();
/ get usermod.message /
pmod = PyImport_ImportModule("usermod");
pdict = PyModule_GetDict(pmod);
pstr = PyRun_String("message", Py_eval_input, pdict, pdict);
/ convert to C /
PyArg_Parse(pstr, "s", &cstr);
printf("%s\n", cstr);
/ assign usermod.X /
PyObject_SetAttrString(pmod, "X", pstr);
/ print usermod.transform(X) /
(void) PyRun_String("print(transform(X))", Py_file_input, pdict, pdict);
Py_DECREF(pmod);
Py_DECREF(pstr);
Py_Finalize();
}
When compiled and run, this file produces the same result as its predecessor:
.../PP4E/Integrate/Embed/Basics$ ./embed-string
embed-string
The meaning of life...
THE MEANING OF PYTHON...However, very different work goes into producing this output. This time, C fetches,
converts, and prints the value of the Python module’s message attribute directly by
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