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<!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) -->
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<title>Boost.Python - <boost/python/exec.hpp></title>
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<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>
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