<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <!-- Copyright David Abrahams 2006. 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) --> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" type="text/css" href="../boost.css"> <title>Boost.Python - <boost/python/exec.hpp></title> </head> <body> <table border="0" cellpadding="7" cellspacing="0" width="100%" summary= "header"> <tr> <td valign="top" width="300"> <h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../boost.png" border="0"></a></h3> </td> <td valign="top"> <h1 align="center"><a href="../index.html">Boost.Python</a></h1> <h2 align="center">Header <boost/python/exec.hpp></h2> </td> </tr> </table> <hr> <h2>Contents</h2> <dl class="page-index"> <dt><a href="#introduction">Introduction</a></dt> <dt><a href="#functions">Functions</a></dt> <dd> <dl class="page-index"> <dt><a href="#eval-spec"><code>eval</code></a></dt> <dt><a href="#exec-spec"><code>exec</code></a></dt> <dt><a href="#exec_file-spec"><code>exec_file</code></a></dt> </dl> </dd> <dt><a href="#examples">Examples</a></dt> </dl> <hr> <h2><a name="introduction"></a>Introduction</h2> <p>Exposes a mechanism for embedding the python interpreter into C++ code.</p> <h2><a name="functions"></a>Functions</h2> <h3><a name="eval-spec"></a><code>eval</code></h3> <pre> object eval(str expression, object globals = object(), object locals = object()); </pre> <dl class="function-semantics"> <dt><b>Effects:</b> Evaluate Python expression from <code>expression</code> in the context specified by the dictionaries <code>globals</code> and <code>locals</code>. </dt> <dt><b>Returns:</b> An instance of <a href="object.html#object-spec">object</a> which holds the value of the expression. </dt> </dl> <h3><a name="exec-spec"></a><code>exec</code></h3> <pre> object exec(str code, object globals = object(), object locals = object()); </pre> <dl class="function-semantics"> <dt><b>Effects:</b> Execute Python source code from <code>code</code> in the context specified by the dictionaries <code>globals</code> and <code>locals</code>. </dt> <dt><b>Returns:</b> An instance of <a href="object.html#object-spec">object</a> which holds the result of executing the code. </dt> </dl> <h3><a name="exec_file-spec"></a><code>exec_file</code></h3> <pre> object exec_file(str filename, object globals = object(), object locals = object()); </pre> <dl class="function-semantics"> <dt><b>Effects:</b> Execute Python source code from the file named by <code>filename</code> in the context specified by the dictionaries <code>globals</code> and <code>locals</code>. </dt> <dt><b>Returns:</b> An instance of <a href="object.html#object-spec">object</a> which holds the result of executing the code. </dt> </dl> <h2><a name="examples"></a>Examples</h2> <para>The following example demonstrates the use of <function>import</function> and <function>exec</function> to define a function in python, and later call it from within C++.</para> <pre> #include <iostream> #include <string> using namespace boost::python; void greet() { // Retrieve the main module. object main = import("__main__"); // Retrieve the main module's namespace object global(main.attr("__dict__")); // Define greet function in Python. object result = exec( "def greet(): \n" " return 'Hello from Python!' \n", global, global); // Create a reference to it. object greet = global["greet"]; // Call it. std::string message = extract<std::string>(greet()); std::cout << message << std::endl; } </pre> <para>Instead of embedding the python script into a string, we could also store it in an a file...</para> <pre> def greet(): return 'Hello from Python!' </pre> <para>... and execute that instead.</para> <pre> // ... // Load the greet function from a file. object result = exec_file(script, global, global); // ... } </pre> <p>Revised 01 November, 2005</p> <p><i>© Copyright Stefan Seefeld 2005.</i></p> </body> </html>