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  4. <title>Chapter&#160;6.&#160;Embedding</title>
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  18. <div class="chapter">
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  19. <div class="titlepage"><div><div><h1 class="title">
    20. 

  20. <a name="embedding"></a>Chapter&#160;6.&#160;Embedding</h1></div></div></div>
    21. 

  21. <div class="toc">
    22. 

  22. <p><b>Table of Contents</b></p>
    23. 

  23. <dl class="toc">
    24. 

  24. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp">boost/python/exec.hpp</a></span></dt>
    25. 

  25. <dd><dl>
    26. 

  26. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.introduction">Introduction</a></span></dt>
    27. 

  27. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_eval">Function
    28. 

  28.         <code class="computeroutput"><span class="identifier">eval</span></code></a></span></dt>
    29. 

  29. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec">Function
    30. 

  30.         <code class="computeroutput"><span class="identifier">exec</span></code></a></span></dt>
    31. 

  31. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec_file">Function
    32. 

  32.         <code class="computeroutput"><span class="identifier">exec_file</span></code></a></span></dt>
    33. 

  33. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.examples">Examples</a></span></dt>
    34. 

  34. </dl></dd>
    35. 

  35. <dt><span class="section"><a href="embedding/boost_python_import_hpp.html">boost/python/import.hpp</a></span></dt>
    36. 

  36. <dd><dl>
    37. 

  37. <dt><span class="section"><a href="embedding/boost_python_import_hpp.html#embedding.boost_python_import_hpp.introduction">Introduction</a></span></dt>
    38. 

  38. <dt><span class="section"><a href="embedding/boost_python_import_hpp.html#embedding.boost_python_import_hpp.function_import">Function
    39. 

  39.         <code class="computeroutput"><span class="identifier">import</span></code></a></span></dt>
    40. 

  40. <dt><span class="section"><a href="embedding/boost_python_import_hpp.html#embedding.boost_python_import_hpp.examples">Examples</a></span></dt>
    41. 

  41. </dl></dd>
    42. 

  42. </dl>
    43. 

  43. </div>
    44. 

  44. <div class="section">
    45. 

  45. <div class="titlepage"><div><div><h2 class="title" style="clear: both">
    46. 

  46. <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>
    47. 

  47. </h2></div></div></div>
    48. 

  48. <div class="toc"><dl class="toc">
    49. 

  49. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.introduction">Introduction</a></span></dt>
    50. 

  50. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_eval">Function
    51. 

  51.         <code class="computeroutput"><span class="identifier">eval</span></code></a></span></dt>
    52. 

  52. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec">Function
    53. 

  53.         <code class="computeroutput"><span class="identifier">exec</span></code></a></span></dt>
    54. 

  54. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.function_exec_file">Function
    55. 

  55.         <code class="computeroutput"><span class="identifier">exec_file</span></code></a></span></dt>
    56. 

  56. <dt><span class="section"><a href="embedding.html#embedding.boost_python_exec_hpp.examples">Examples</a></span></dt>
    57. 

  57. </dl></div>
    58. 

  58. <div class="section">
    59. 

  59. <div class="titlepage"><div><div><h3 class="title">
    60. 

  60. <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>
    61. 

  61. </h3></div></div></div>
    62. 

  62. <p>
    63. 

  63.           Exposes a mechanism for embedding the python interpreter into C++ code.
    64. 

  64.         </p>
    65. 

  65. </div>
    66. 

  66. <div class="section">
    67. 

  67. <div class="titlepage"><div><div><h3 class="title">
    68. 

  68. <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
    69. 

  69.         <code class="computeroutput"><span class="identifier">eval</span></code></a>
    70. 

  70. </h3></div></div></div>
    71. 

  71. <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>
    72. 

  72.             <span class="identifier">object</span> <span class="identifier">globals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">(),</span>
    73. 

  73.             <span class="identifier">object</span> <span class="identifier">locals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">());</span>
    74. 

  74. </pre>
    75. 

  75. <div class="variablelist">
    76. 

  76. <p class="title"><b></b></p>
    77. 

  77. <dl class="variablelist">
    78. 

  78. <dt><span class="term">Effects</span></dt>
    79. 

  79. <dd><p>
    80. 

  80.                 Evaluate Python expression from expression in the context specified
    81. 

  81.                 by the dictionaries globals and locals.
    82. 

  82.               </p></dd>
    83. 

  83. <dt><span class="term">Returns</span></dt>
    84. 

  84. <dd><p>
    85. 

  85.                 An instance of object which holds the value of the expression.
    86. 

  86.               </p></dd>
    87. 

  87. </dl>
    88. 

  88. </div>
    89. 

  89. </div>
    90. 

  90. <div class="section">
    91. 

  91. <div class="titlepage"><div><div><h3 class="title">
    92. 

  92. <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
    93. 

  93.         <code class="computeroutput"><span class="identifier">exec</span></code></a>
    94. 

  94. </h3></div></div></div>
    95. 

  95. <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>
    96. 

  96.             <span class="identifier">object</span> <span class="identifier">globals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">(),</span>
    97. 

  97.             <span class="identifier">object</span> <span class="identifier">locals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">());</span>
    98. 

  98. </pre>
    99. 

  99. <div class="variablelist">
    100. 

  100. <p class="title"><b></b></p>
    101. 

  101. <dl class="variablelist">
    102. 

  102. <dt><span class="term">Effects</span></dt>
    103. 

  103. <dd><p>
    104. 

  104.                 Execute Python source code from code in the context specified by
    105. 

  105.                 the dictionaries globals and locals.
    106. 

  106.               </p></dd>
    107. 

  107. <dt><span class="term">Returns</span></dt>
    108. 

  108. <dd><p>
    109. 

  109.                 An instance of object which holds the result of executing the code.
    110. 

  110.               </p></dd>
    111. 

  111. </dl>
    112. 

  112. </div>
    113. 

  113. </div>
    114. 

  114. <div class="section">
    115. 

  115. <div class="titlepage"><div><div><h3 class="title">
    116. 

  116. <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
    117. 

  117.         <code class="computeroutput"><span class="identifier">exec_file</span></code></a>
    118. 

  118. </h3></div></div></div>
    119. 

  119. <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>
    120. 

  120.                  <span class="identifier">object</span> <span class="identifier">globals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">(),</span>
    121. 

  121.                  <span class="identifier">object</span> <span class="identifier">locals</span> <span class="special">=</span> <span class="identifier">object</span><span class="special">());</span>
    122. 

  122. </pre>
    123. 

  123. <div class="variablelist">
    124. 

  124. <p class="title"><b></b></p>
    125. 

  125. <dl class="variablelist">
    126. 

  126. <dt><span class="term">Effects</span></dt>
    127. 

  127. <dd><p>
    128. 

  128.                 Execute Python source code from the file named by filename in the
    129. 

  129.                 context specified by the dictionaries globals and locals.
    130. 

  130.               </p></dd>
    131. 

  131. <dt><span class="term">Returns</span></dt>
    132. 

  132. <dd><p>
    133. 

  133.                 An instance of object which holds the result of executing the code.
    134. 

  134.               </p></dd>
    135. 

  135. </dl>
    136. 

  136. </div>
    137. 

  137. </div>
    138. 

  138. <div class="section">
    139. 

  139. <div class="titlepage"><div><div><h3 class="title">
    140. 

  140. <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>
    141. 

  141. </h3></div></div></div>
    142. 

  142. <p>
    143. 

  143.           The following example demonstrates the use of import and exec to define
    144. 

  144.           a function in python, and later call it from within C++.
    145. 

  145.         </p>
    146. 

  146. <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
    147. 

  147. <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span>
    148. 

  148. 

  149. <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>
    150. 

  150. 

  151. <span class="keyword">void</span> <span class="identifier">greet</span><span class="special">()</span>
    152. 

  152. <span class="special">{</span>
    153. 

  153.   <span class="comment">// Retrieve the main module.</span>
    154. 

  154.   <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>
    155. 

  155. 

  156.   <span class="comment">// Retrieve the main module's namespace</span>
    157. 

  157.   <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>
    158. 

  158. 

  159.   <span class="comment">// Define greet function in Python.</span>
    160. 

  160.   <span class="identifier">object</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">exec</span><span class="special">(</span>
    161. 

  161.     <span class="string">"def greet():                   \n"</span>
    162. 

  162.     <span class="string">"   return 'Hello from Python!' \n"</span><span class="special">,</span>
    163. 

  163.     <span class="identifier">global</span><span class="special">,</span> <span class="identifier">global</span><span class="special">);</span>
    164. 

  164. 

  165.   <span class="comment">// Create a reference to it.</span>
    166. 

  166.   <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>
    167. 

  167. 

  168.   <span class="comment">// Call it.</span>
    169. 

  169.   <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>
    170. 

  170.   <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>
    171. 

  171. <span class="special">}</span>
    172. 

  172. </pre>
    173. 

  173. <p>
    174. 

  174.           Instead of embedding the python script into a string, we could also store
    175. 

  175.           it in an a file...
    176. 

  176.         </p>
    177. 

  177. <pre class="programlisting"><span class="identifier">def</span> <span class="identifier">greet</span><span class="special">():</span>
    178. 

  178.    <span class="keyword">return</span> <span class="char">'Hello from Python!'</span>
    179. 

  179. </pre>
    180. 

  180. <p>
    181. 

  181.           ... and execute that instead.
    182. 

  182.         </p>
    183. 

  183. <pre class="programlisting">  <span class="comment">// ...</span>
    184. 

  184.   <span class="comment">// Load the greet function from a file.</span>
    185. 

  185.   <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>
    186. 

  186.   <span class="comment">// ...</span>
    187. 

  187. <span class="special">}</span>
    188. 

  188. </pre>
    189. 

  189. </div>
    190. 

  190. </div>
    191. 

  191. </div>
    192. 

  192. <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
    193. 

  193. <td align="left"></td>
    194. 

  194. <td align="right"><div class="copyright-footer">Copyright &#169; 2002-2005, 2015 David Abrahams, Stefan Seefeld<p>
    195. 

  195.         Distributed under the Boost Software License, Version 1.0. (See accompanying
    196. 

  196.         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>
    197. 

  197.       </p>
    198. 

  198. </div></td>
    199. 

  199. </tr></table>
    200. 

  200. <hr>
    201. 

  201. <div class="spirit-nav">
    202. 

  202. <a accesskey="p" href="to_from_python_type_conversion/boost_python_register_ptr_to_pyt.html"><img src="../images/prev.png" alt="Prev"></a><a accesskey="u" href="index.html"><img src="../images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../images/home.png" alt="Home"></a><a accesskey="n" href="embedding/boost_python_import_hpp.html"><img src="../images/next.png" alt="Next"></a>
    203. 

  203. </div>
    204. 

  204. </body>
    205. 

  205. </html>
    206.