Hi! I've been using the boost::python library for some time with few problems but now I got stuck. Fortunately I isolated the problem. In the class Domain below I defined a property called solver which returns a shared_ptr<Solver> instance: *namespace bp=boost::python;** **class Solver **{ **public: ** bool _b; ** void func() { _b = true; } **};** **typedef shared_ptr<Solver> Solver_ptr;** ** class Domain **{ **public: ** Solver_ptr solver; ** void set_solver(Solver_ptr s) { solver = s; } **};** **typedef shared_ptr<Domain> Domain_ptr;** ** BOOST_PYTHON_MODULE(test) {** * * bp::class_<Solver, Solver_ptr>("Solver")* * .def("func", &Solver::func)* * ;* * bp::class_<Domain, Domain_ptr>("Domain")* * .def("set_solver" , &Domain::set_solver)* * .add_property("solver" , &Domain::solver)* * ;* *}* The code compiles ok. The problem appears while running in Python: *from test import * **d = Domain() **s = Solver() **d.set_solver(s) # is it ok to do that? **d.solver.func() # this line does not work* With the following error message: *Traceback (most recent call last):* * File "test_test.py", line 5, in <module>* * d.solver.func()* *Boost.Python.ArgumentError: Python argument types in* * Solver.func(Solver)* *did not match C++ signature:* * func(Solver {lvalue})* I suspect that the problem is related with add_property returning a shared_ptr<Solver> aka Solver_ptr. It seems that add_property is returning a *non lvalue* Solver object. I tried applying return value policies with no luck. How can I get Domain::solver with type Solver_ptr in Python as a lvalue ? Thanks! Raul Durand