Mailman 3 August 2010 - Cplusplus-sig

boost::python embedding error - runtime - Mac OS X - 1.38
by Igor Karpov Oct. 1, 2014

Oct. 1, 2014

Hi, I am trying to run the following program: #include <iostream> #include <Python.h> #include <boost/python.hpp> using namespace boost::python; using namespace std; int main(int argc, char** argv) { { // Using Python/C Py_Initialize(); PyObject* main_module = PyImport_ImportModule("__main__"); PyObject* globals = PyEval_GetGlobals(); PyObject* locals = PyEval_GetLocals(); PyRun_SimpleString("print 'Hello World, from Python/C!'\n"); Py_Finalize(); } { // Using boost::python Py_Initialize(); object main_module = import("__main__"); object main_namespace = main_module.attr("__dict__"); try { object ignored = exec("print 'Hello World, from boost::python!'\n", main_namespace); Py_Finalize(); } catch (error_already_set const& e) { PyErr_Print(); return 1; } } return 0; } on Linux (both x86 and x86_64), with Ubuntu's default version of Boost (1.34.1) installed, I am able to do so as expected: $ ./embed Hello World, from Python/C! Hello World, from boost::python! on Mac OS X, I get a runtime error: $ ./embed Hello World, from Python/C! Bus Error Running with gdb, this is the stack trace: Hello World, from Python/C! Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_PROTECTION_FAILURE at address: 0x00000000 0x00000000 in ?? () (gdb) where #0 0x00000000 in ?? () #1 0x00bb618f in PyEval_GetGlobals () #2 0x00bce0dd in PyImport_Import () #3 0x00bce2b0 in PyImport_ImportModule () #4 0x008127d4 in boost::python::import (name=@0xbffff4a8) at libs/python/src/import.cpp:20 #5 0x00004446 in main (argc=1, argv=0xbffff510) at embed.cc:22 For this Mac, boost version is latest (1.38) and python version is: Python 2.5.4 (r254:67917, Dec 23 2008, 14:57:27) [GCC 4.0.1 (Apple Computer, Inc. build 5363)] on darwin Is this a bug? I attached the source and the cmake file I am using to build, for convenience. Thanks, --Igor.

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CMake and getting starting with boost.python
by Braddock Gaskill Aug. 5, 2011

Aug. 5, 2011

Yesterday I became a boost.python user, after years of heavy SWIG usage. I would have started using boost.python years ago except for the bjam learning curve. I spent hours TRYING on multiple occasions, but got lost every time trying to get the page one example to build with bjam. Here is how to build the "greet" example with a four line CMake file: cat >>CMakeLists.txt <<EOF LINK_LIBRARIES(boost_python) INCLUDE_DIRECTORIES("/usr/include/python2.5") LINK_DIRECTORIES("/usr/lib/python2.5") # Not needed? ADD_LIBRARY(hello SHARED hello.cpp) EOF You WILL have to `mv libhello.so hello.so` after building. Works for me under Ubuntu Linux 6.10 after apt-get install cmake python2.5-dev boost-python-dev cmake make mv libhello.so hello.so ipython In [1]: import hello In [2]: hello.greet() Out[2]: 'hello, world' Boost.Python has been a joy to learn and use since I got past bjam. I had a moderately large API wrapped in just my first couple hours of learning (less time than I spent messing with bjam). Any additional advice for using CMake to build boost.python? Braddock Gaskill

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How to import a boost::python dll in windows?
by ichijoji Aug. 5, 2011

Aug. 5, 2011

I'm trying to port some research code that uses boost::python to expose a library to python to windows, but I'm having trouble importing the dll into python. I'm compiling using msvc 2005 and using python 2.5, but when I try to import the module I get this: Traceback (most recent call last): File "main.py", line 1, in <module> import object File "c:\code\sge\code\scripts\object.py", line 1, in <module> import sge ImportError: No module named sge My module is named sge and I'm compiling to sge.dll. Is there some obvious reason why python wouldn't be able to find my dll? When I compile on linux into an so this code works fine. -- View this message in context: http://www.nabble.com/How-to-import-a-boost%3A%3Apython-dll-in-windows--tf3… Sent from the Python - c++-sig mailing list archive at Nabble.com.

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Miscellaneous Boost.Python Utilities
by Jim Bosch July 6, 2011

July 6, 2011

In the hope that others might find them useful, and perhaps contribute some of their own, I've posted a collection of miscellaneous Boost.Python extensions I've been using at the Boost sandbox: http://svn.boost.org/svn/boost/sandbox/python_extensions Features include: - Conversions between STL containers and Boost.Range iterator ranges and Python builtins like list, tuple, and dict. - Conversions between Boost.Fusion sequences and Python tuples. - A third solution to the const shared_ptr problem (see http://language-binding.net/pyplusplus/troubleshooting_guide/shared_ptr/sha…) that isn't evil (I don't think) and doesn't involve changing the Boost.Python library itself - it simply doesn't use register_ptr_to_python to register the conversion. More info is available in the README file. Also, I'm sure many of the regulars on this list have their own similar extensions, and I'd love to see them collected in one place. If you'd like to add your collection to mine, or have a suggestion for some other place I should put my collection, please let me know. I would like to limit this collection to simple things that don't depend on non-Boost libraries, however. Jim Bosch

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question about object
by Junwei Zhang Sept. 1, 2010

Sept. 1, 2010

Hi all, who can tell me what c++ semantics of following statement. I do not understand it, it do not like usual c++ codes object msg="%s is bigger than %s" %make_tuple(NAME,name); -- Junwei Zhang Office Phone:402-472-1968 junweizhang2006(a)gmail.com www.junweizhang.com Department of Electrical Engineering University of Nebraska-Lincoln 209N Walter Scott Engineering Center P.O. Box 880511 Lincoln, NE 68588-0511

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boost.python import problem
by Junwei Zhang Aug. 30, 2010

Aug. 30, 2010

Hi, everyone, I just started study boost.python. and have following problem /boostpy.cc #include <boost/python.hpp> char const* greet() { return "hello, world"; } BOOST_PYTHON_MODULE(boostpy) { using namespace boost::python; def("greet", greet); } g++ boostpy.cc -lpython2.5 -I /usr/include/python2.5 -o boostpy.so -shared It complies ,but when import it in python, I have following error, <<<import boostpy Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: ./boostpy.so: undefined symbol: _ZN5boost6python6detail11init_ moduleEPKcPFvvE any suggestion? Thanks -- Junwei Zhang Office Phone:402-472-1968 junweizhang2006(a)gmail.com www.junweizhang.com Department of Electrical Engineering University of Nebraska-Lincoln 209N Walter Scott Engineering Center P.O. Box 880511 Lincoln, NE 68588-0511 -- Junwei Zhang Office Phone:402-472-1968 junweizhang2006(a)gmail.com www.junweizhang.com Department of Electrical Engineering University of Nebraska-Lincoln 209N Walter Scott Engineering Center P.O. Box 880511 Lincoln, NE 68588-0511

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registering the same type converter in different modules with Boost.Python
by Changsheng Jiang Aug. 30, 2010

Aug. 30, 2010

Hi, list I have to convert std::pair to python tuple in different modules independently. And these modules may be used concurrently, importing the second module will report an warning like "std::pair has been already registered". How to fixed the warning and registered the same type in different modules correctly? thanks. Changsheng Jiang

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Strange boost::python::object behaviour
by Marek Denis Aug. 27, 2010

Aug. 27, 2010

Hello everybody, This is my first post on this mailing group so I wanted to say hello to all ml users ;) I am encounetring a strange problem with boost::python::object in my module. What I want to achieve is a module written in C++ with use of the boost::python, that can be imported to normal python application. Python classes would do some additional parsing and put everything into the database. However, in my C++ code I would like to launch a few methods from the instances of the classes that were defined in the Python code (different module). From the python point of view it should look like this: #v+ m=cppmodule.cppclass()() t=pythonmodule.pythonclass() m.register_callback(t) m.start() #v- and the 'm' instance should start it's work however invoking some methods of the 't' instance. What I did was writing a method in my C++ code, something like: #v+ void Manager::register_callback(boost::python::object& obj) { this->callback = obj; for(int i=0;i<5;++i) { std::cout << "Callback P()" << endl; callback.attr("p")(); } return; } #v- This is supposed to save an object to my C++ class so that I can use it later ( this->callback = obj; ) I did some tests, by invoking some 'test' method of the Python object (method called 'p'), that just prints some string. It does work when I invoke register_callback method. However, later in code, when I invoke other method, say (for tests now): #v+ void Manager::test() { callback.attr("p")(); return; } #v- I get the "segmentation fault". I should admit, that the callback variable is inside the global instance of the Manager object, none of the objects are deleted. Where should I look for a solution, what do I wrong? Thanks in advance! -- pozdrawiam Marek Denis

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converting a PyObject into its C-Type
by Erik Tuerke Aug. 27, 2010

Aug. 27, 2010

Hi! I am trying to convert a PyObject into its C-Type. The thing is, i have a function which takes a PyObject but i need to convert the PyObject into its respective C-Type. For example i have a python class: class_<isis::util::fvector4, _Vector4<float> >("py_fvector4", init<float, float, float, float>()) .def( init<>()) .def("__setitem__", &_Vector4<float>::setItem) .def("__getitem__", &_Vector4<float>::getItem) ; How can i convert the PyObject "py_fvector4" back into its C-Type _Vector4 (or isis::util::fvector4) ? Thanks for your help and best regards! -- Erik Tuerke Department of Neurophysics Max-Planck-Institute for Human Cognitive and Brain Sciences Stephanstrasse 1A 04103 Leipzig Germany Tel: +49 341 99 40-2440 Email: tuerke(a)cbs.mpg.de www.cbs.mpg.de

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Does Py_Initialize change CTRL-C behaviour?
by David Aldrich Aug. 25, 2010

Aug. 25, 2010

Hi We have just added Py_Initialize() and Py_Finalize() calls to our C++ application, in order to support embedded Python. Our's is a console application. We have noticed the side effect that CTRL-C no longer terminates the application. This is true for both Linux and Windows builds. Is this a known behaviour of Py_Initialize() ? Is there any way to reinstate normal CTRL-C handling? Best regards David

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