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POUnable to access C++ class method exposed using boost python
 

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  1. POUnable to access C++ class method exposed using boost python
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    <p>I am new to Python and currently trying to expose some C++ APIs to Python using boost.python.</p> <p>I started with a simple class that is close to what i'm trying to achieve:</p> <pre><code>class BaseImpl { public: BaseImpl() {} virtual int f() { return 10; } }; class BaseImplWrap : public BaseImpl, public wrapper&lt;BaseImpl&gt; { public: int f() { return this-&gt;get_override("f")(); } }; </code></pre> <p>And exposed as follows:</p> <pre><code>BOOST_PYTHON_MODULE(test) { class_&lt;BaseImplWrap, boost::noncopyable&gt;("BaseImpl", init&lt;&gt;()) .def("f", &amp;BaseImpl::f) ; } </code></pre> <p>When I tried to access the exposed class method on PythonWin, I get the following error:</p> <pre><code>PythonWin 2.7 (r27:82525, Jul 4 2010, 07:43:08) [MSC v.1500 64 bit (AMD64)] on win32. Portions Copyright 1994-2008 Mark Hammond - see 'Help/About PythonWin' for further copyright information. &gt;&gt;&gt; import test &gt;&gt;&gt; a=test.BaseImpl() &gt;&gt;&gt; a.fFailed to format the args Traceback (most recent call last): File "C:\Program Files\Python\Lib\site-packages\pythonwin\pywin\idle\CallTips.py", line 130, in get_arg_text argText = inspect.formatargspec(*arg_getter(fob)) File "C:\Program Files\Python\lib\inspect.py", line 813, in getargspec raise TypeError('{!r} is not a Python function'.format(func)) TypeError: &lt;Boost.Python.function object at 0x000000000533ADF0&gt; is not a Python function </code></pre> <p>I then tried something simpler from the <a href="https://wiki.python.org/moin/boost.python/ExportingClasses" rel="nofollow">Exporting Class</a> tutorial, but still can't get it working with the following error:</p> <pre><code>namespace { class hello { public: hello(const std::string&amp; country) { this-&gt;country = country; } std::string greet() const { return "Hello from " + country; } private: std::string country; }; } BOOST_PYTHON_MODULE(test) { class_&lt;hello&gt;("hello", init&lt;std::string&gt;()) .def("greet", &amp;hello::greet) // Add a regular member function. ; } &gt;&gt;&gt; import test &gt;&gt;&gt; a=test.hello('world') &gt;&gt;&gt; a.greetFailed to format the args Traceback (most recent call last): File "C:\Program Files\Python\Lib\site-packages\pythonwin\pywin\idle\CallTips.py", line 130, in get_arg_text argText = inspect.formatargspec(*arg_getter(fob)) File "C:\Program Files\Python\lib\inspect.py", line 813, in getargspec raise TypeError('{!r} is not a Python function'.format(func)) TypeError: &lt;Boost.Python.function object at 0x0000000002FEACA0&gt; is not a Python function </code></pre> <p>Any idea why the exposed class methods are not recognized as python function? Is it something to do with my system configurations?</p> <p>I'm running on a <strong>Window 7 x64 machine</strong>, with <strong>Python 2.7</strong>, <strong>boost 1.54.0</strong> and <strong>MSVC 2012 x64</strong>.</p> <p>Thanks in advance.</p>
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    1. COthe constructor for `hello` takes a `std::string` as an argument which you are not providing in your python code. Try this: `a=test.hello('USA')`
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      1. POUnable to access C++ class method exposed using boost python
      1. USGareth
    2. COHi Gareth, thanks for pointing out the mistake. I tried that and run into the same error when accessing a.greet(): TypeError: ... is not a Python function. Any idea?
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    3. COLooks to me like a pythonwin error. Would you try in a command line interface ?
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      1. USRaffi
 

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