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3<!-- Copyright David Abrahams 2006. Distributed under the Boost -->
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13    <title>Boost.Python - &lt;boost/python/scope.hpp&gt;</title>
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16  <body>
17    <table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
18    "header">
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22          alt="C++ Boost" src="../../../../boost.png" border="0"></a></h3>
23        </td>
24
25        <td valign="top">
26          <h1 align="center"><a href="../index.html">Boost.Python</a></h1>
27
28          <h2 align="center">Header &lt;boost/python/scope.hpp&gt;</h2>
29        </td>
30      </tr>
31    </table>
32    <hr>
33
34    <h2>Contents</h2>
35
36    <dl class="page-index">
37      <dt><a href="#introduction">Introduction</a></dt>
38
39      <dt><a href="#classes">Classes</a></dt>
40
41      <dd>
42        <dl class="page-index">
43          <dt><a href="#scope-spec">Class <code>scope</code></a></dt>
44
45          <dd>
46            <dl class="page-index">
47              <dt><a href="#scope-spec-synopsis">Class <code>scope</code>
48              synopsis</a></dt>
49
50              <dt><a href="#scope-spec-ctors">Class <code>scope</code>
51              constructors and destructor</a></dt>
52            </dl>
53          </dd>
54        </dl>
55      </dd>
56
57      <dt><a href="#examples">Example</a></dt>
58    </dl>
59    <hr>
60
61    <h2><a name="introduction"></a>Introduction</h2>
62
63    <p>Defines facilities for querying and controlling the Python scope
64    (namespace) which will contain new wrapped classes and functions.</p>
65
66    <h2><a name="classes"></a>Classes</h2>
67
68    <h3><a name="scope-spec"></a>Class <code>scope</code></h3>
69
70    <p>The <code>scope</code> class has an associated global Python
71    object which controls the Python namespace in which new extension
72    classes and wrapped functions will be defined as
73    attributes. Default-constructing a new <code>scope</code> object
74    binds it to the associated global Python object. Constructing a
75    <code>scope</code> object with an argument changes the associated
76    global Python object to the one held by the argument, until the
77    lifetime of the <code>scope</code> object ends, at which time the
78    associated global Python object reverts to what it was before the
79    <code>scope</code> object was constructed.</p>
80
81    <h4><a name="scope-spec-synopsis"></a>Class <code>scope</code>
82    synopsis</h4>
83<pre>
84namespace boost { namespace python
85{
86  class scope : public <a href=
87"object.html#object-spec">object</a>
88  {
89   public:
90      scope(scope const&amp;);
91      scope(object const&amp;);
92      scope();
93      ~scope()
94   private:
95      void operator=(scope const&amp;);
96  };
97}}
98</pre>
99
100    <h4><a name="scope-spec-ctors"></a>Class <code>scope</code> constructors
101    and destructor</h4>
102<pre>
103explicit scope(scope const&amp; x);
104explicit scope(object const&amp; x);
105</pre>
106    Stores a reference to the current associated scope object, and sets the
107    associated scope object to the one referred to by <code>x.ptr()</code>.
108    The <code>object</code> base class is initialized with <code>x</code>.
109<pre>
110scope();
111</pre>
112    Stores a reference to the current associated scope object. The
113    <code>object</code> base class is initialized with the current associated
114    scope object. Outside any module initialization function, the current
115    associated Python object is <code>None</code>.
116<pre>
117~scope()
118</pre>
119    Sets the current associated Python object to the stored object.
120
121    <h2><a name="examples"></a>Example</h2>
122    The following example shows how scope setting can be used to define
123    nested classes.
124
125    <p>C++ Module definition:</p>
126<pre>
127#include &lt;boost/python/module.hpp&gt;
128#include &lt;boost/python/class.hpp&gt;
129#include &lt;boost/python/scope.hpp&gt;
130using namespace boost::python;
131
132struct X
133{
134  void f() {}
135
136  struct Y { int g() { return 42; } };
137};
138
139BOOST_PYTHON_MODULE(nested)
140{
141   // add some constants to the current (module) scope
142   scope().attr("yes") = 1;
143   scope().attr("no") = 0;
144
145   // Change the current scope
146   scope outer
147       = class_&lt;X&gt;("X")
148            .def("f", &amp;X::f)
149            ;
150
151   // Define a class Y in the current scope, X
152   class_&lt;X::Y&gt;("Y")
153      .def("g", &amp;X::Y::g)
154      ;
155}
156</pre>
157    Interactive Python:
158<pre>
159&gt;&gt;&gt; import nested
160&gt;&gt;&gt; nested.yes
1611
162&gt;&gt;&gt; y = nested.X.Y()
163&gt;&gt;&gt; y.g()
16442
165</pre>
166
167    <p>Revised 09 October, 2002</p>
168
169    <p><i>&copy; Copyright <a href=
170    "../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p>
171  </body>
172</html>
173
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