Hello, I've tried to adapt using myfm = boost::container::flat_map<const T*, V>; with boost::python::map_indexing_suite class_< myfm, myfm* >("myfm") .def( map_indexing_suite<myfm>{} ) ; I get a compile errors: /usr/include/boost/python/detail/invoke.hpp:75:14: error: no match for call

to ‘(const boost::python::detail::specify_a_return_value_policy_to_wrap_functions_returning<const T*>) (const T*)’ ... Caller = boost::python::detail::caller<const T* (*)(std::pair<const T*, V>&), default_call_policies ...>

I would suspect that there is some function that returns the key_type of the flat_map and takes a single argument of the value_type, but I can't find any. If there's one, I would need pick a return value policy for it. MM