gistfile1.py

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

using namespace std;

namespace py = boost::python;

std::string parse_python_exception(){
    PyObject *type_ptr = NULL, *value_ptr = NULL, *traceback_ptr = NULL;
    // Fetch the exception info from the Python C API
    PyErr_Fetch(&type_ptr, &value_ptr, &traceback_ptr);

    // Fallback error
    std::string ret("Unfetchable Python error");
    // If the fetch got a type pointer, parse the type into the exception string
    if(type_ptr != NULL){
        py::handle<> h_type(type_ptr);
        py::str type_pstr(h_type);
        // Extract the string from the boost::python object
        py::extract<std::string> e_type_pstr(type_pstr);
        // If a valid string extraction is available, use it
        // otherwise use fallback
        if(e_type_pstr.check())
            ret = e_type_pstr();
        else
            ret = "Unknown exception type";
    }
    // Do the same for the exception value (the stringification of the exception)
    if(value_ptr != NULL){
        py::handle<> h_val(value_ptr);
        py::str a(h_val);
        py::extract<std::string> returned(a);
        if(returned.check())
            ret += ": " + returned();
        else
            ret += std::string(": Unparseable Python error: ");
    }
    // Parse lines from the traceback using the Python traceback module
    if(traceback_ptr != NULL){
        py::handle<> h_tb(traceback_ptr);
        // Load the traceback module and the format_tb function
        py::object tb(py::import("traceback"));
        py::object fmt_tb(tb.attr("format_tb"));
        // Call format_tb to get a list of traceback strings
        py::object tb_list(fmt_tb(h_tb));
        // Join the traceback strings into a single string
        py::object tb_str(py::str("\n").join(tb_list));
        // Extract the string, check the extraction, and fallback in necessary
        py::extract<std::string> returned(tb_str);
        if(returned.check())
            ret += ": " + returned();
        else
            ret += std::string(": Unparseable Python traceback");
    }
    return ret;
}


void getServices(vector<pair<string, string> > & ret) {
    try {
        Py_Initialize();
        char* argv = (char*) "";
        PySys_SetArgv(0, &argv);
        py::object main_module = py::import("__main__");
        // load the dictionary object out of the main module
        py::object main = main_module.attr("__dict__");
        // load functions
        py::exec("import rosservice", main);
        py::object get_service_list = py::eval("rosservice.get_service_list", main);
        py::object get_service_type = py::eval("rosservice.get_service_type", main);
        // do look-ups
        py::object srv_list = get_service_list();

        for(int i=0; i<py::len(srv_list); i++) {
            std::string s = py::extract<std::string>(srv_list[i]);
            py::object t_obj = get_service_type(s);
            std::string t = py::extract<std::string>(t_obj);
            ret.emplace_back(s,t);
        }
    } catch(py::error_already_set const&) {
        string perror_str = parse_python_exception();
        cout << "Error in Python: " << perror_str << endl;
    }
}