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POBoost.Python - How to re-enter module scope?
 

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  1. POBoost.Python - How to re-enter module scope?
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    <p>I'm exposing some C++ classes to Python that have nested <code>enum</code>'s. Looking at the example documentation at <a href="http://www.boost.org/doc/libs/1_48_0/libs/python/doc/tutorial/doc/html/python/object.html" rel="nofollow">boost.org</a> and <a href="http://wiki.python.org/moin/boost.python/module" rel="nofollow">wiki.python.org</a>, I can't see how to leave a scope once it has been entered, in order to go back to the global / module scope. Instead, each subsequent scope gets nested within the previous one.</p> <p>As an example:</p> <pre class="lang-cpp prettyprint-override"><code>#include &lt;boost/python.hpp&gt; class Foo { public: enum Choose { eFoo, eBar }; /* Default constructor with enum as required argument */ Foo(Choose choice): m_choice(choice) {} ~Foo() {} Choose get() const { return m_choice; } private: const Choose m_choice; }; class Bar { }; BOOST_PYTHON_MODULE(foo) { using namespace boost::python; scope global; /* Define Foo class, and a scope to go with it. */ scope in_Foo = class_&lt;Foo&gt; ("Foo", init&lt;Foo::Choose&gt;()) .def("rovalue", &amp;Foo::get) ; /* Expose 'Choose' enum as Foo.Choose */ enum_&lt;Foo::Choose&gt;("Choose") .value("Foo", Foo::eFoo) .value("Bar", Foo::eBar) ; /* How to get back to module scope?? */ global; scope(); /* This currently is exposed as Foo.Bar, but should just be Bar */ class_&lt;Bar&gt;("Bar", init&lt;&gt;()) ; } </code></pre> <p>I've tried changing that <code>global;</code> line to various things, but all to the same result:</p> <pre class="lang-bash prettyprint-override"><code>$ g++ -fPIC -shared scope.cpp -o foo.so -lpython2.7 -I/usr/include/python2.7 -lboost_python $ python -c 'import foo; print "Bar" in dir(foo)' False $ python -c 'import foo; print "Bar" in dir(foo.Foo)' True </code></pre> <p><strong>EDIT:</strong></p> <p>Having had another look at wiki.python.org, it would seem that in the above example, the correct answer would be to use <code>scope within(global)</code> to revert to the module level scope. Indeed, this works for the above example. Unfortunately however, I get a compile error when I use it in my actual application..</p> <pre><code>#include &lt;boost/python.hpp&gt; using namespace boost; BOOST_PYTHON_MODULE(foo) { python::scope module_level; /* .... */ python::scope python::within(module_level); /* ... */ } </code></pre> <p>Compile error:</p> <pre><code>error: invalid use of qualified-name 'boost::python::within' </code></pre>
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