libs/python/test/pickle3.cpp
// Copyright Ralf W. Grosse-Kunstleve 2002-2004. Distributed under the Boost
// Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
/*
This example shows how to make an Extension Class "pickleable".
The world class below contains member data (secret_number) that
cannot be restored by any of the constructors. Therefore it is
necessary to provide the __getstate__/__setstate__ pair of pickle
interface methods.
The object's __dict__ is included in the result of __getstate__.
This requires more code (compare with pickle2.cpp), but is
unavoidable if the object's __dict__ is not always empty.
For more information refer to boost/libs/python/doc/pickle.html.
*/
#include <boost/python/module.hpp>
#include <boost/python/def.hpp>
#include <boost/python/class.hpp>
#include <boost/python/tuple.hpp>
#include <boost/python/dict.hpp>
#include <boost/python/extract.hpp>
#include <boost/python/back_reference.hpp>
namespace boost_python_test {
// A friendly class.
class world
{
public:
world(const std::string& _country) : secret_number(0) {
this->country = _country;
}
std::string greet() const { return "Hello from " + country + "!"; }
std::string get_country() const { return country; }
void set_secret_number(int number) { secret_number = number; }
int get_secret_number() const { return secret_number; }
private:
std::string country;
int secret_number;
};
struct world_pickle_suite : boost::python::pickle_suite
{
static
boost::python::tuple
getinitargs(const world& w)
{
return boost::python::make_tuple(w.get_country());
}
static
boost::python::tuple
getstate(boost::python::object w_obj)
{
world const& w = boost::python::extract<world const&>(w_obj)();
return boost::python::make_tuple(
w_obj.attr("__dict__"),
w.get_secret_number());
}
static
void
setstate(boost::python::object w_obj, boost::python::tuple state)
{
using namespace boost::python;
world& w = extract<world&>(w_obj)();
if (len(state) != 2)
{
PyErr_SetObject(PyExc_ValueError,
("expected 2-item tuple in call to __setstate__; got %s"
% state).ptr()
);
throw_error_already_set();
}
// restore the object's __dict__
dict d = extract<dict>(w_obj.attr("__dict__"))();
d.update(state[0]);
// restore the internal state of the C++ object
long number = extract<long>(state[1]);
if (number != 42)
w.set_secret_number(number);
}
static bool getstate_manages_dict() { return true; }
};
}
BOOST_PYTHON_MODULE(pickle3_ext)
{
using namespace boost_python_test;
boost::python::class_<world>(
"world", boost::python::init<const std::string&>())
.def("greet", &world::greet)
.def("get_secret_number", &world::get_secret_number)
.def("set_secret_number", &world::set_secret_number)
.def_pickle(world_pickle_suite())
;
}