Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Click here to view the latest version of this page.

Boost.Python

Header <boost/python/data_members.hpp>

Contents

Introduction
Functions
make_getter
make_setter
Example

Introduction

make_getter() and make_setter() are the functions used internally by class_<>::def_readonly and class_<>::def_readwrite to produce Python callable objects which wrap C++ data members.

Functions

template <class C, class D>
object make_getter(D C::*pm);

template <class C, class D, class Policies>
object make_getter(D C::*pm, Policies const& policies);
Requires: Policies is a model of CallPolicies.
Effects: Creates a Python callable object which accepts a single argument that can be converted from_python to C*, and returns the corresponding member D member of the C object, converted to_python. If policies is supplied, it will be applied to the function as described here. Otherwise, the library attempts to determine whether D is a user-defined class type, and if so uses return_internal_reference<>
for Policies. Note that this test may inappropriately choose return_internal_reference<> in some cases when D is a smart pointer type. This is a known defect.
Returns: An instance of object which holds the new Python callable object.
template <class D>
object make_getter(D const& d);
template <class D, class Policies>
object make_getter(D const& d, Policies const& policies);

template <class D>
object make_getter(D const* p);
template <class D, class Policies>
object make_getter(D const* p, Policies const& policies);
Requires: Policies is a model of CallPolicies.
Effects: Creates a Python callable object which accepts no arguments and returns d or *p, converted to_python on demand. If policies is supplied, it will be applied to the function as described here. Otherwise, the library attempts to determine whether D is a user-defined class type, and if so uses reference_existing_object
for Policies.
Returns: An instance of object which holds the new Python callable object.
template <class C, class D>
object make_setter(D C::*pm);

template <class C, class D, class Policies>
object make_setter(D C::*pm, Policies const& policies);
Requires: Policies is a model of CallPolicies.
Effects: Creates a Python callable object which, when called from Python, expects two arguments which can be converted from_python to C* and D const&, respectively, and sets the corresponding D member of the C object. If policies is supplied, it will be applied to the function as described here.
Returns: An instance of object which holds the new Python callable object.
template <class D>
object make_setter(D& d);
template <class D, class Policies>
object make_setter(D& d, Policies const& policies);

template <class D>
object make_setter(D* p);
template <class D, class Policies>
object make_setter(D* p, Policies const& policies);
Requires: Policies is a model of CallPolicies.
Effects: Creates a Python callable object which accepts one argument, which is converted from Python to D const& and written into d or *p, respectively. If policies is supplied, it will be applied to the function as described here.
Returns: An instance of object which holds the new Python callable object.

Example

The code below uses make_getter and make_setter to expose a data member as functions:

#include <boost/python/data_members.hpp>
#include <boost/python/module.hpp>
#include <boost/python/class.hpp>

struct X
{
    X(int x) : y(x) {}
    int y;
};

using namespace boost::python;

BOOST_PYTHON_MODULE_INIT(data_members_example)
{
    class_<X>("X", init<int>())
       .def("get", make_getter(&X::y))
       .def("set", make_setter(&X::y))
       ;
}
It can be used this way in Python:
>>> from data_members_example import *
>>> x = X(1)
>>> x.get()
1
>>> x.set(2)
>>> x.get()
2

5 August, 2003

© Copyright Dave Abrahams 2002.