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# Boost.Python

## Header <call.hpp>

## Contents

Introduction
Functions

call

Example(s)

## Introduction

`<boost/python/call.hpp>` defines the `call` family of overloaded function templates, used to invoke Python callable objects from C++.

## Functions

    template <class R, class A1, class A2, ... class An>
    R call(PyObject* callable, A1 const&, A2 const&, ... An const&)

Requires: `R` is a pointer type, reference type, or a complete type with an accessible copy constructor
Effects: Invokes `callable(a1, a2, ...an)` in Python, where `a1`...`an` are the arguments to `call()`, converted to Python objects.
Returns: The result of the Python call, converted to the C++ type `R`.
Rationale: For a complete semantic description and rationale, see this page.

## Example(s)

The following C++ function applies a Python callable object to its two arguments and returns the result. If a Python exception is raised or the result can't be converted to a `double`, an exception is thrown.

    double apply2(PyObject* func, double x, double y)
    {
       return boost::python::call<double>(func, x, y);
    }

Revised 9 May, 2002

© Copyright Dave Abrahams 2002.