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Redirecting embedded Python’s I/O

Posted on 2012-4-13 by mvasilkov
When using Python for application scripting, more often than not you want to redirect interpreter’s input/output to the embedding program. This is how it’s done with the Python/C API:

PyObject *sys = PyImport_ImportModule("sys");
PyObject *out = PyFile_FromString("python_out", "w+");
PyObject_SetAttrString(sys, "stdout", out);
Pretty intuitive, right? Now embedded Python’s stdout points to the newly created file, python_out. Working with the script’s output from C is also trivial:

FILE *output = PyFile_AsFile(out);
rewind(output);

int c = fgetc(output);
/* fgets(), fread(), any function that takes (FILE*) */
The output stream can be reset to the initial (empty) state like this:

ftruncate(fileno(output), 0);
Redirecting stdin is left as an exercise to the reader.