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POexposing std::vector<double> with boost.python
 

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    <p>I have written some C++ code that generates a std::vector.</p> <p>I also have a python script that manipulates some data that, for now, I am declaring like this (below). </p> <pre><code>import numpy x = numpy.random.randn(1000) y = numpy.random.randn(1000) </code></pre> <p>I can run the script fine. From my C++ code:</p> <pre><code> using namespace boost::python; try{ Py_Initialize(); object main = import("__main__"); object global(main.attr("__dict__")); object result = exec_file("scatterPlot.py", global, global); Py_Finalize(); } catch(error_already_set){ PyErr_Print(); } return; </code></pre> <p>I have no idea how to get my C++ data to python. I've around quite a bit, but there doesn't seem to be anything definitive.</p> <p>I have in my C++</p> <pre><code>BOOST_PYTHON_MODULE(vector_indexing_suite_ext){ boost::python::class_&lt;std::vector&lt;double&gt; &gt;("PyVec") .def(boost::python::vector_indexing_suite&lt;std::vector&lt;double&gt; &gt;()); } </code></pre> <p>This seems to work, but as I understand, it only provides a class "PyVec" for my python script but not the data I need. Am I wrong?</p> <p>I've also seen some other people use <a href="http://aspn.activestate.com/ASPN/Mail/Message/cpp-sig/3786737" rel="nofollow noreferrer">boost::shared_ptr in a python mailing list</a>. </p> <p>I also found <a href="http://thread.gmane.org/gmane.comp.python.c++/12004/focus=12011" rel="nofollow noreferrer">this example</a> but found it confusing.</p> <p>I can think of a few approaches</p> <ol> <li>Pass something to the <code>boost::python::exec_file</code> method</li> <li>Using the <code>boost_indexing_suite_ext</code></li> <li>Uinsg <code>boost::shared_ptr</code></li> </ol> <p>Which approach is easiest to get going? No approach seems clear to me.</p> <p>Here are some more links I've looked at: <a href="http://www.boost.org/doc/libs/1_41_0/libs/python/doc/tutorial/doc/html/python/embedding.html" rel="nofollow noreferrer">from the boost website</a> <a href="http://wiki.python.org/moin/boost.python/HowTo#std.3A.3AC.2B-.2B-container" rel="nofollow noreferrer">from the python website</a> <a href="http://old.nabble.com/-python--Expose-a-struct-with-a-std::vector&lt;std::string&gt;-member-td21809375.html" rel="nofollow noreferrer">another mailing list thread</a></p> <p>UPDATE:</p> <p>This works for passing an <code>int</code> to my python code like below</p> <pre><code>int main(){ int five_squared=0; int a =3; try { Py_Initialize(); object main_module = import("__main__"); object main_namespace = main_module.attr("__dict__"); main_namespace["var"]=a; object ignored = exec("result = 5 ** var", main_namespace); five_squared = extract&lt;int&gt;(main_namespace["result"]); } catch( error_already_set ) { PyErr_Print(); } std::cout &lt;&lt; five_squared &lt;&lt; std::endl; return 0; } </code></pre> <p>But I want to pass a vector, when I try to do that in a similar fashion as above I get this error</p> <blockquote> <p>TypeError: No to_python (by-value) converter found for C++ type: std::vector ></p> </blockquote> <p>So, obviously I need to tell python how to deal with std::vector. I think this code could help with that.</p> <pre><code>BOOST_PYTHON_MODULE(vector_indexing_suite_ext){ boost::python::class_&lt;std::vector&lt;double&gt; &gt;("PyVec") .def(boost::python::vector_indexing_suite&lt;std::vector&lt;double&gt; &gt;()); } </code></pre> <p>But since std::vector is pretty common, there must be a defined way to do this... right?</p>
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