Using boost::python, how to return vector of structs as list of dicts to Python?

Question

I have the following C++ code:

    struct MyType { int x, y; };
    struct A { 
        std::vector<MyType> get_data();
    };

which I want to interface to Python using Boost Python so that it can be used in the following way:

    a = A()
    ret = a.get_data();
    for r in ret:
        print('x=%d; y=%d;' % (r['x'], r['y']))

What I have now is a rather naive:

    BOOST_PYTHON_MODULE(pyA) { 
        class_<A>("A").def("get_data", &A::get_data);
    }

which gives me, as expected, the following error

     TypeError: No to_python (by-value) converter found for C++ type

when I try to call the get_data() function from the Python code.

I have seen posts on here (such as std::vector to boost::python::list) which describe how to use vector_indexing_suite to convert a std::vector<T> to a list for some types T (e.g. floats, strings), but I'm not sure how to extend this to deal with my struct -> dict conversion as well. Any help would be greatly appreciated.

Answer 1

In the end I adopted a solution like the following, which I post here in case it is useful to somebody else in the future. This can be improved by adding boost's "readonly" qualifier, but I haven't done so yet.

#include <boost/python.hpp>
using namespace boost::python;

struct Point { 
    int x, y;
};

using Points = std::vector<Point>;

struct Converter
{
    static PyObject* convert(const Points& v)
    {
        boost::python::list ret;
        for (const auto& c : v) {
            boost::python::dict *r = new boost::python::dict();
            (*r)["x"] = c.x;
            (*r)["y"] = c.y;
            ret.append(boost::python::object(*r));
         }
        return boost::python::incref(ret.ptr());
    }
};

BOOST_PYTHON_MODULE(mymodule)
{
    boost::python::to_python_converter<Points, Converter>();

    class_<MyClass, boost::noncopyable>("MyClass")
        .def("get_data", &MyClass::get_data);
}