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<title>Chapter 6. Embedding</title>
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<div class="chapter">
<div class="titlepage"><div><div><h1 class="title">
<a name="embedding"></a>Chapter 6. Embedding</h1></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<dl class="toc">
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp">boost/python/exec.hpp</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.introduction">Introduction</a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_eval">Function
<code class="computeroutput"><span class="identifier">eval</span></code></a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec">Function
<code class="computeroutput"><span class="identifier">exec</span></code></a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec_file">Function
<code class="computeroutput"><span class="identifier">exec_file</span></code></a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.examples">Examples</a></span></dt>
</dl></dd>
<dt><span class="section"><a href="embedding/boost_python_import_hpp.html">boost/python/import.hpp</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="embedding/boost_python_import_hpp.html#embedding.boost_python_import_hpp.introduction">Introduction</a></span></dt>
<dt><span class="section"><a href="embedding/boost_python_import_hpp.html#embedding.boost_python_import_hpp.function_import">Function
<code class="computeroutput"><span class="identifier">import</span></code></a></span></dt>
<dt><span class="section"><a href="embedding/boost_python_import_hpp.html#embedding.boost_python_import_hpp.examples">Examples</a></span></dt>
</dl></dd>
</dl>
</div>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="embedding.boost_python_exec_hpp"></a><a class="link" href="embedding.html#embedding.boost_python_exec_hpp" title="boost/python/exec.hpp">boost/python/exec.hpp</a>
</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.introduction">Introduction</a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_eval">Function
<code class="computeroutput"><span class="identifier">eval</span></code></a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec">Function
<code class="computeroutput"><span class="identifier">exec</span></code></a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec_file">Function
<code class="computeroutput"><span class="identifier">exec_file</span></code></a></span></dt>
<dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.examples">Examples</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="embedding.boost_python_exec_hpp.introduction"></a><a class="link" href="embedding.html#embedding.boost_python_exec_hpp.introduction" title="Introduction">Introduction</a>
</h3></div></div></div>
<p>
Exposes a mechanism for embedding the python interpreter into C++ code.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="embedding.boost_python_exec_hpp.function_eval"></a><a class="link" href="embedding.html#embedding.boost_python_exec_hpp.function_eval" title="Function eval">Function
<code class="computeroutput"><span class="identifier">eval</span></code></a>
</h3></div></div></div>
<pre class="programlisting"><span class="identifier">object</span> <span class="identifier">eval</span><span class="special">(</span><span class="identifier">str</span> <span class="identifier">expression</span><span class="special">,</span>
<span class="identifier">object</span> <span class="identifier">globals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">(),</span>
<span class="identifier">object</span> <span class="identifier">locals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">());</span>
</pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Effects</span></dt>
<dd><p>
Evaluate Python expression from expression in the context specified
by the dictionaries globals and locals.
</p></dd>
<dt><span class="term">Returns</span></dt>
<dd><p>
An instance of object which holds the value of the expression.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="embedding.boost_python_exec_hpp.function_exec"></a><a class="link" href="embedding.html#embedding.boost_python_exec_hpp.function_exec" title="Function exec">Function
<code class="computeroutput"><span class="identifier">exec</span></code></a>
</h3></div></div></div>
<pre class="programlisting"><span class="identifier">object</span> <span class="identifier">exec</span><span class="special">(</span><span class="identifier">str</span> <span class="identifier">code</span><span class="special">,</span>
<span class="identifier">object</span> <span class="identifier">globals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">(),</span>
<span class="identifier">object</span> <span class="identifier">locals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">());</span>
</pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Effects</span></dt>
<dd><p>
Execute Python source code from code in the context specified by
the dictionaries globals and locals.
</p></dd>
<dt><span class="term">Returns</span></dt>
<dd><p>
An instance of object which holds the result of executing the code.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="embedding.boost_python_exec_hpp.function_exec_file"></a><a class="link" href="embedding.html#embedding.boost_python_exec_hpp.function_exec_file" title="Function exec_file">Function
<code class="computeroutput"><span class="identifier">exec_file</span></code></a>
</h3></div></div></div>
<pre class="programlisting"><span class="identifier">object</span> <span class="identifier">exec_file</span><span class="special">(</span><span class="identifier">str</span> <span class="identifier">filename</span><span class="special">,</span>
<span class="identifier">object</span> <span class="identifier">globals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">(),</span>
<span class="identifier">object</span> <span class="identifier">locals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">());</span>
</pre>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">Effects</span></dt>
<dd><p>
Execute Python source code from the file named by filename in the
context specified by the dictionaries globals and locals.
</p></dd>
<dt><span class="term">Returns</span></dt>
<dd><p>
An instance of object which holds the result of executing the code.
</p></dd>
</dl>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="embedding.boost_python_exec_hpp.examples"></a><a class="link" href="embedding.html#embedding.boost_python_exec_hpp.examples" title="Examples">Examples</a>
</h3></div></div></div>
<p>
The following example demonstrates the use of import and exec to define
a function in python, and later call it from within C++.
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span>
<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">python</span><span class="special">;</span>
<span class="keyword">void</span> <span class="identifier">greet</span><span class="special">()</span>
<span class="special">{</span>
<span class="comment">// Retrieve the main module.</span>
<span class="identifier">object</span> <span class="identifier">main</span> <span class="special">=</span> <span class="identifier">import</span><span class="special">(</span><span class="string">"__main__"</span><span class="special">);</span>
<span class="comment">// Retrieve the main module's namespace</span>
<span class="identifier">object</span> <span class="identifier">global</span><span class="special">(</span><span class="identifier">main</span><span class="special">.</span><span class="identifier">attr</span><span class="special">(</span><span class="string">"__dict__"</span><span class="special">));</span>
<span class="comment">// Define greet function in Python.</span>
<span class="identifier">object</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">exec</span><span class="special">(</span>
<span class="string">"def greet(): \n"</span>
<span class="string">" return 'Hello from Python!' \n"</span><span class="special">,</span>
<span class="identifier">global</span><span class="special">,</span> <span class="identifier">global</span><span class="special">);</span>
<span class="comment">// Create a reference to it.</span>
<span class="identifier">object</span> <span class="identifier">greet</span> <span class="special">=</span> <span class="identifier">global</span><span class="special">[</span><span class="string">"greet"</span><span class="special">];</span>
<span class="comment">// Call it.</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">message</span> <span class="special">=</span> <span class="identifier">extract</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;(</span><span class="identifier">greet</span><span class="special">());</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">message</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
Instead of embedding the python script into a string, we could also store
it in an a file...
</p>
<pre class="programlisting"><span class="identifier">def</span> <span class="identifier">greet</span><span class="special">():</span>
<span class="keyword">return</span> <span class="char">'Hello from Python!'</span>
</pre>
<p>
... and execute that instead.
</p>
<pre class="programlisting"> <span class="comment">// ...</span>
<span class="comment">// Load the greet function from a file.</span>
<span class="identifier">object</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">exec_file</span><span class="special">(</span><span class="identifier">script</span><span class="special">,</span> <span class="identifier">global</span><span class="special">,</span> <span class="identifier">global</span><span class="special">);</span>
<span class="comment">// ...</span>
<span class="special">}</span>
</pre>
</div>
</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2015 David Abrahams, Stefan Seefeld<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>
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