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May 2017

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Cannot import the Hello World module of Boost.Python's QuickStart in python
by Heng Zhou May 26, 2017

May 26, 2017

I followed the steps in the QuickStart of Boost.Python here: https://urldefense.proofpoint.com/v2/url?u=http-3A__www.boost.org_doc_libs_… . I can successfully compile, link and get the output dll file, but I always got and error: Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: No module named hello_ext when trying to import it in python. This is my environment: - Windows 7 Enterprise SP1 64 bit, I am the Administrator and run cmd as Administrator. - Python 2.7.13 64 bit - Visual Studio 2015 (v14.0) Update 3 - In VS2015, the project name is ConsoleApplication1, so the output is ConsoleApplication1.dll. - I built the simple sample code under x64 configuration in VS2015 and I verified with dumpbin that the output ConsoleApplication1.dll is really 64 bit. I tried the following but got the same error: - I added the search path to the ConsoleApplication1.dll into sys.path - I changed the name of ConsoleApplication1.dll to hello_ext.dll The QuickStart says "The resulting DLL is now visible to Python." but that magic does not take place on my machine. Could you please tell me what I had missed or, if I built the DLL properly, how to import it in python command line? Thanks a lot.

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LNK2019 Unresolved External Symbol in VS2015 when using Boost python3 and numpy3 libraries on Windows
by Øystein Skotheim May 22, 2017

May 22, 2017

I have downloaded and built Boost 1.64 on Windows by using the following command: b2 --build-type=complete address-model=64 toolset=msvc stage I added a user-config.jam file in my home directory to tell Boost where to find Python 3: using python : 3.6 : c:\\anaconda3\\python ; I am then trying to compile a small test project using boost::python and boost::numpy: #include <boost/python.hpp> #include <boost/python/numpy.hpp> namespace bp = boost::python; namespace np = boost::python::numpy; np::ndarray test_make_zeros(int rows, int cols) { return np::zeros(bp::make_tuple(rows, cols), np::dtype::get_builtin<float>()); } BOOST_PYTHON_MODULE(test_boost_python) { np::initialize(); bp::def("test_make_zeros", test_make_zeros); } I am using the following CMakeLists.txt file: cmake_minimum_required(VERSION 3.8) project(test_boost_python) set(BOOST_ROOT "C:/Boost-1.64") set(Boost_ADDITIONAL_VERSIONS 1.64) find_package(PythonLibs 3.6 REQUIRED) include_directories(${PYTHON_INCLUDE_DIRS}) find_package(Boost REQUIRED COMPONENTS python3 numpy3) include_directories(${Boost_INCLUDE_DIRS}) link_directories(${Boost_LIBRARY_DIRS}) add_library(test_boost_python SHARED test_boost_python.cpp) set_target_properties(test_boost_python PROPERTIES PREFIX "" SUFFIX ".pyd") set_target_properties(test_boost_python PROPERTIES DEFINE_SYMBOL "BOOST_ALL_NO_LIB") target_link_libraries(test_boost_python ${PYTHON_LIBRARIES} ${Boost_LIBRARIES}) My boost::python library is given the name boost_python3-vc140-mt-1_64.lib and boost::numpy ends up as boost_numpy3-vc140-mt-1_64.lib when linking against Python 3.6. I had to turn on BOOST_ALL_NO_LIB. If not, the compiler looks for boost_python-vc140-mt-1_64.lib boost_numpy-vc140-mt-1_64.lib (which is under the wrong name, with a missing number 3 after the library names - Is this a bug on Windows?) For my test project, I now get the following linking error: test_boost_python.obj : error LNK2019: unresolved external symbol "class boost::python::numpy::dtype __cdecl boost::python::numpy::detail::get_float_dtype<32>(void)" (??$get_float_dtype@$0CA@@detail@numpy@python@boost@@YA?AVdtype@123@XZ) referenced in function "public: static class boost::python::numpy::dtype __cdecl boost::python::numpy::detail::builtin_dtype<float,0>::get(void)" (?get@?$builtin_dtype@M$0A@@detail@numpy@python@boost@@SA?AVdtype@345@XZ) What may be the reason for this missing symbol and how should I go about to fix it? -Øystein

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