Boost.Python

Contents

Introduction

Functions

make_function

make_constructor

Example

Introduction

make_function() and make_constructor() are the functions used internally by class_<>::def, class_<>::def, and class_<>::def_init to produce Python callable objects which wrap C++ functions and member functions.

Functions

template <class F>
objects::function* make_function(F f)</a>

template <class F, class Policies>
objects::function* make_function(F f, Policies const& policies)

Requires: F is a function pointer or member function pointer type

Effects: Creates a Python callable object which, when called from Python, converts its arguments to C++ and calls f. If F is a pointer-to-member-function type, the target object of the function call (*this) will be taken from the first Python argument, and subsequent Python arguments will be used as the arguments to f. If policies are supplied, it must be a model of CallPolicies, and will be applied to the function as described here.

Returns: A pointer convertible to PyObject* which refers to the new Python callable object.

template <class T, class ArgList, class Generator>
objects::function* make_constructor();

Requires: T is a class type. ArgList is an MPL sequence of C++ argument types (A1, A2,... AN) such that if a1, a2... aN are objects of type A1, A2,... AN respectively, the expression new Generator::apply<T>::type(a1, a2... aN) is valid. Generator is a model of HolderGenerator.

Effects: Creates a Python callable object which, when called from Python, expects its first argument to be a Boost.Python extension class object. It converts its remaining its arguments to C++ and passes them to the constructor of a dynamically-allocated Generator::apply<T>::type object. The result is installed in the extension class object.

Returns: The new Python callable object

Example

C++ function exposed below returns a callable object wrapping one of two functions.

#include <boost/python/make_function.hpp>
#include <boost/python/module.hpp>

char const* foo() { return "foo"; }
char const* bar() { return "bar"; }

PyObject* choose_function(bool selector)
{
    if (selector)
        return boost::python::make_function(foo);
    else
        return boost::python::make_function(bar);
}

BOOST_PYTHON_MODULE_INIT(make_function_test)
{
    module("make_function_test")
        .def("choose_function", choose_function);
}

>>> from make_function_test import *
>>> f = choose_function(1)
>>> g = choose_function(0)
>>> f()
'foo'
>>> g()
'bar'

14 February 2002

© Copyright Dave Abrahams 2002. All Rights Reserved.