How can I get output of PyErr_Print in windows or save it as a string

Question

I am writing embedded python interpretor, there is a function PyErr_Print() (https://docs.python.org/3/c-api/exceptions.html) which writes to standard error text explaining why C function I called failed.

This doesn't seem to work on windows as it never writes anything to terminal, is there a way to redirect it somewhere, or store as a string so that I can see it?

Answer 1

Here is a solution using boost::python:

#include <ostream>
#include <boost/python.hpp>

std::ostream& operator<<(std::ostream& os, boost::python::error_already_set& e) {
  using namespace boost::python;
  // acquire the Global Interpreter Lock

  PyObject * extype, * value, * traceback;
  PyErr_Fetch(&extype, &value, &traceback);
  if (!extype) return os;

  object o_extype(handle<>(borrowed(extype)));
  object o_value(handle<>(borrowed(value)));
  object o_traceback(handle<>(borrowed(traceback)));

  object mod_traceback = import("traceback");
  object lines = mod_traceback.attr("format_exception")(
    o_extype, o_value, o_traceback);

  for (int i = 0; i < len(lines); ++i)
    os << extract<std::string>(lines[i])();

  // PyErr_Fetch clears the error state, uncomment
  // the following line to restore the error state:
  // PyErr_Restore(extype, value, traceback);

  // release the GIL
  return os;
}

Use like this:

#include <iostream>
#include <boost/python.hpp>

try {
   // some code that raises
catch (boost::python::error_already_set& e) {
   std::cout << e << std::endl; // or stream to somewhere else
}