I've been puzzling around about how to deal with converting my string type to/from Python. I've managed to get one part of the puzzle solved, but can't work out from the documentation what the other part is. The code I have so far is this: namespace { struct to_pystr { static PyObject *convert( const fostlib::string &s ) { std::wstring u( fostlib::coerce< std::wstring >( s ) ); return PyUnicode_FromWideChar( u.c_str(), u.length() ); } static PyTypeObject const* get_pytype() { return &PyUnicode_Type; } }; } BOOST_PYTHON_MODULE( crypto ) { using namespace boost::python; // fostlib::string fostlib::sha1( const fostlib::string& ) def( "sha1", fostlib::sha1 ); implicitly_convertible< fostlib::native_string, fostlib::string >(); to_python_converter< fostlib::string, to_pystr, false >(); } This works ok if the Python type is str, but it doesn't work for unicode strings: Boost.Python.ArgumentError: Python argument types in crypto.sha1(unicode) did not match C++ signature: sha1(fostlib::string) What I guess I need is some way to wrap the Python call PyUnicode_FromObject in order to construct my string type, probably from PyObject, but certainly from unicode. From the documentation at [1] it isn't at all clear what actually needs to be done -- I can't even tell from that what the function signature I need to code to is. I think this [2] is relevant, but can't work out in what way -- no mention is made of where the reference object comes from and nor is there an example of the implementation of a simple extractor concept -- the internal implementations of the ones given on the page are far from illuminating. [1]http://www.boost.org/doc/libs/1_36_0/libs/python/doc/v2/Extractor.html [2]http://www.boost.org/doc/libs/1_36_0/libs/python/doc/v2/lvalue_from_pytype.h... It looks like there's some good emails linked from this page [3], but unfortunately the links to the Python list archives are broken. [3]http://www.boost.org/doc/libs/1_36_0/libs/python/doc/internals.html I did think about exposing my string class, but the __unicode__ operator doesn't seem to be supported. Adding it to the relevant Boost.Python headers doesn't appear to be enough to get it working and I don't think that is the right way to do this either. So, basically, I guess there ought to be a fairly simple way to add this sort of type conversion into the Boost.Python type registry, but it appears to be undocumented and I can't see anything for this in the examples or the tests in the library either. K