Mailman 3 March 2019 - Cplusplus-sig

GSOC 2019 Boost.Python
by Damika Gamlath March 27, 2019

March 27, 2019

Hi, I am Damika Gamlath an undergraduate from Department of Computer Science & Engineering, University of Moratuwa, Sri Lanka. I am interested to participate in GSOC 2019. I would like to know about project ideas under Boost.Python. Further I would like to be guided about next steps. Thank you! Best regards, Damika Gamlath

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Linking issues with Boost.Python 1.69.0, Python 2.7, MSVC 14.0
by Sarah Rust March 27, 2019

March 27, 2019

Hello! I have been trying to build and link the latest Boost.Python to work with Python 2.7 and my Visual Studio 2015 project (MSVC 14.0) with x64 configuration. I've added the Boost library and Boost include directory to my project's properties, but I am getting the following error when I create a BOOST_PYTHON_MODULE: error LNK2001: unresolved external symbol "__declspec(dllimport) struct _object * __cdecl boost::python::detail::init_module(char const *,void (__cdecl*)(void))" (__imp_?init_module@detail@python@boost@@YAPEAU_object@ @PEBDP6AXXZ@Z) Please let me know how others are doing this. Thanks, Sarah

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argument conversion of numpy.int64 to double
by Pavol Juhas March 26, 2019

March 26, 2019

Hello, After wrapping a simple C++ function of a double argument with boost python, I have noticed it crashes when called from Python with a numpy.int64 value. This is a likely situation, for example when evaluated for values from numpy.arange. Please see below for a minimum example. Is there some simple way of telling the wrapper how to handle numpy.int64 arguments? BTW, I have noticed that the boost/numpy library sets up several scalar converters on its initialization - this happens in boost/python/numpy.hpp <https://github.com/boostorg/python/blob/6f72675bff276599ffdccb9681018d8b2e3…> and then in the register_scalar_converters <https://github.com/boostorg/python/blob/6f72675bff276599ffdccb9681018d8b2e3…> function. However, adding a call to boost::python::numpy::initialize did not make a difference in my example. Thank you for any advice. Best, Pavol // dbfunction.cpp ------------------------------------------------------------ #include <boost/python/module.hpp> #include <boost/python/def.hpp> #include <boost/python/numpy.hpp> double duplicate(double x) { return 2 * x; } BOOST_PYTHON_MODULE(dbfunction) { using boost::python::def; // no difference with line below // boost::python::numpy::initialize(); def("duplicate", duplicate); } // --------------------------------------------------------------------------- # TEST $ python -c 'import dbfunction, numpy; dbfunction.duplicate(numpy.int64(0))' Traceback (most recent call last): File "<string>", line 1, in <module> Boost.Python.ArgumentError: Python argument types in dbfunction.duplicate(numpy.int64) did not match C++ signature: duplicate(double)

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GSOC
by virali vora March 21, 2019

March 21, 2019

Hi, I went through the project details of Boost Python-C++ integeration and found them quite interesting. I would like to contribute to the project. The project says that we need to implement a c++ interface for Python' set type. So, should that include all the set methods of Python? Also, is there any discussion channel where I can communicate with you? Thanks.

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Fail to build Boost Python Tutorial: LNK1120: 55 unresolved externals
by Markus Johann Schmidt March 20, 2019

March 20, 2019

Dear all, I try to learn boost and in particular the Python extension part. But I am already failing with building the tutorial. I am quite a beginner with compiling in C++ I use a Win10 64bit System. I have to use VS2015, because for a proprietary library I have to compile later in msvc120 (64bit). VS2017 is installed on the computer as well. I tried to following for compilation 1. Launch the "Developer Command Prompt for VS2015" 2. Setting Python environment: "C:\Users\schmmark\Anaconda3\Scripts\activate.bat" "C:\Users\schmmark\Anaconda3\envs\py36" 3. cd C:\Users\schmmark\Downloads\boost_1_69_0\boost_1_69_0 4. bootstrap.bat (successful) 5. b2.exe toolset=msvc-14.0 address-model=64 (successful) 6. cd libs\python\example\tutorial 7. ..\..\..\..\bjam.exe toolset=msvc-14.0 address-model=64 --debug-configuration I modified the Jamfile from tutorial folder and Jamroot from example folder as can be found in the attachment. I get the error `hello_ext.pyd : fatal error LNK1120: 55 unresolved externals` A complete output of my command prompt is attached as well. May my problem be * wrong import of python library? I try to use a wildcard in lib boost_python instead of `boost_python36-vc140-mt-x64-1_69` But the error stays the same when I rename it * Some issues with 32bit and 64bit detection? * Am I missing some imports? Thanks in advance for your support Markus

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Calling python function repr from C++ using boost.python (possible?)
by Jones, Torrin A (US) March 10, 2019

March 10, 2019

Is it possible to call repr from C++ on a C++ object that can be converted to python? Let me explain. I have an enum that I converted to python using boost::python::enum_(). That class already provides a good repr() to python (thanks to the boost::python developers for that). However that enum is used as a type on a member in another C++ class that I have where boost::python does not provide a good repr(). So I'm trying to provide one and thought, it sure would be nice if I could just call repr() on the member. I assume I have to convert the value on that member to python first, some kind of way then call repr? Is that possible? Or is there a better way? Example: Typedef enum { V1 = 0, V2 = 5, V3 = 6 } values; Class ValueExample { Public: ValueExample(const values& v) {m_value = v}; Values getValue() const { return m_value }; Private: Values m_value; } Std::string ValueExampleRepr(const ValueExample& object) { Std::stringstream ss; // What do I put here? // Ss << repr(object.getValue()); Return ss::str(); } Boost::python::enum_<values> values("values"); Values.value("V1", V1); Values.value("V2", V2); Values.value("V3", V3); Boost::python::class_<ValueExample> ValueExample("ValueExample"); ValueExample("__repr__", ValueExampleRepr);

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