Mailman 3 July 2011 - 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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Wrap std::vector<pointer*>
by Simon W Aug. 3, 2011

Aug. 3, 2011

>From my research it seems not very trivial to wrap std::vector that holds pointer types. For example: std::vector<GameObject*> I've looked at boost python vector_index_suite but it just gives me the runtime error: > TypeError: No to_python (by-value) converter found for C++ type: > GameObject* I have already exposed GameObject: class_<GameObject>(" GameObject") ... So it have come to my understanding it's not possible with an out of the box solution. I have to do some kind of wrapper? Could someone just help me out where I should start? Thank you!

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Abstract class instances to-python conversion
by Valentin Perrelle Aug. 2, 2011

Aug. 2, 2011

Hi, I'm currently embedding and extending Python using Boost.Python. I'm trying to expose some c++ library (OIS) classes to my Python scripts. This library mainly exposes abstract classes since the actual implementation are derived classes specialized for each operating system. So, i have to wrap those abstract classes. Then, eventually i will convert some existing C++ object of this class to its Python equivalent. Ideally, I would think that the HeldType is a pointer to the existing C++ object. There is no pointer managment problem since the lifetime of the object is greater than the execution time of the script. There is probably something i don't understand in the design of Boost.Python. At this point, my problem is that i need a to_python conversion which requires the abscence of noncopyable attribute which then implies to be able to build an instance of the object (which i cannot provide since the class is abstract, and i don't have any concrete derived class). I don't yet understand why holding a pointer in the Python object requires the ability to build instances of the wrapped class. The exact compile-time error i get is: boost_1_44/boost/python/object/pointer_holder.hpp:194:14: error: cannot allocate an object of abstract type 'OIS::Keyboard' I'm using boost 1.44 (required by some other library) Python 3.2 and MinGW/Msys. Module declaration: BOOST_PYTHON_MODULE(OIS) { class_<Keyboard, Keyboard*>("Keyboard", no_init); } Python init: try { PyImport_AppendInittab("OIS", PyInit_OIS); Py_InitializeEx(0); object main(import("__main__")); dict globals(main.attr("__dict__")); globals["keyboard"] = ptr(keyboard); } catch (error_already_set&) { PyErr_Print(); } Did i choose the wrong desing ? Did i do something wrong ? What should i do to solve this problem ? Valentin Perrelle.

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create module in embedded python
by Horváth Imre July 30, 2011

July 30, 2011

Hi! I want to create a python module in embedded python from string (The module script is stored in a database). My code looks like this: command.py: class Command: def execute(self): return "foo" main.cpp: #include <iostream> #include <fstream> #include <boost/python.hpp> int main(int argc, char **argv) { Py_Initialize(); try { // read the Command class std::stringstream buffer; std::ifstream ifile("command.py"); buffer << ifile.rdbuf(); ifile.close(); boost::python::str command_class(buffer.str()); // create module boost::python::object py_module_new = boost::python::import("new"); boost::python::object module = py_module_new.attr("module")("testmodule"); boost::python::object module_namespace = module.attr("__dict__"); // add Command class to the module boost::python::exec(command_class, module_namespace); // test Command boost::python::object command = module.attr("Command")(); boost::python::object r = command.attr("execute")(); std::string value = boost::python::extract<std::string>(r); std::cout << value << std::endl; } catch(...) { PyErr_Print(); PyErr_Clear(); } Py_Finalize(); return 0; } It works as expected. But when I add and import command to the command.py file, it fails: command.py: import math class Command: def execute(self): return "foo" The error is: Traceback (most recent call last): File "<string>", line 1, in <module> ImportError: __import__ not found What am I missing? Thanks in advance: Imre Horvath

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Cannot import .pyd generated using Boost.Python on Windows XP using Mingw
by Richard Starfield July 28, 2011

July 28, 2011

Hi, I tried building the hello world tutorial example using bjam and it seemed to pass the tests - the generated hello.output file contains: > hello, world > > EXIT STATUS: 0 However when I copy the resulting hello_ext.pyd to the Python DLL directory and try to >>> import hello_ext within Python, I get the message "ImportError: DLL load failed: The specified module could not be found." How do I fix this? Thanks, Richard.

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wrap C++ function with private copy constructor
by Manuela Kaelberer July 24, 2011

July 24, 2011

Hi, I have to wrap a C++ API for Python. There are a couplt of difficulties: - The C++ classes have private constructors. - pointers to class instances are parameters for functions - callbacks that are initiated by the C++ side, but call functions implemented on the Python side. How do I do that? Any hint is appreciated. Example: class X { public: X(); virtual ~X(); virtual callback(A* a) = 0; }; class Y::X { Y(); ~Y(); callback(A* a); } class M { public: M(); virtual ~M() protected: M(const M& m); M & operator=(const M& m); } class N::M { public: N() virtual ~N() private N(const N& n); N& operator=(const N& n); } class A: { public: A(); protected: A(const A& a); A& operator=(const A& a) } class B::A { public: B(); void create(Y* y, M* m); private: B(const B& b); B& operator=(const B& b); }; ===================================================== Python: class Y: __init__(): pass def callback(a): print "callback implemented in python" y=Y() n=N() b=B() b.create(y, n) The callback function y.callback(A* a) will be called by the C++ API when an event occurs. Kind Regards Manuela Kaelberer ---------------------------------------------- Manuela Kälberer IT FM Consulting (1432 H) Landesbank Baden-Württemberg Am Hauptbahnhof 2 D-70173 Stuttgart Phone +49 711 127-43753 Fax +49 711 127-437 59 manuela.kaelberer(a)LBBW.de www.LBBW.de Landesbank Baden-Wuerttemberg Anstalt des oeffentlichen Rechts Hauptsitze: Stuttgart, Karlsruhe, Mannheim, Mainz HRA 12704 Amtsgericht Stuttgart

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boost testing uses non-existing location
by Alexey Akimov July 10, 2011

July 10, 2011

Dear all, I encountered the following problem. When I compile and try to run the python extension with bjam and boost.testing suite the latter tries to use the previous location of my python installation. As it follows from the output the testing suit tries to run this version of python --> /users/aa7/Python_m64/bin/python2.6, but before installing it there I had similar version of python installed in here --> /users/aa7/bin. The last location was then completely removed, so now I am trying to use the former one. However, it looks like boost have remembered the previous location and tries to invoke the python executable from there too. This is obvious from the following line of the output: "/users/aa7/Python_m64/bin/python2.6" "/users/aa7/bin" "test.py" > ... I do not have and /users/aa7/bin directory at all. What should I change to get rid of referencing to that directory? Or how should I fix the problem? So here is the most informative part of the output: .... gcc.link.dll bin/gcc-4.1.2/release/address-model-64/myextension.so capture-output bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext ====== BEGIN OUTPUT ====== /users/aa7/Python_m64/bin/python2.6: can't open file '/users/aa7/bin': [Errno 2] No such file or directory EXIT STATUS: 2 ====== END OUTPUT ====== LD_LIBRARY_PATH=/users/aa7/Soft/boost_1_39_0/bin.v2/libs/python/build/gcc-4.1.2/release/address-model-64:/users/aa7/Soft/boost_1_39_0/bin.v2/libs/regex/build/gcc-4.1.2/release/address-model-64:/users/aa7/Soft/boost_1_39_0/libs/python/example/MyExtension/bin/gcc-4.1.2/release/address-model-64:/usr/bin:/usr/lib:/usr/lib32:/usr/lib64:$LD_LIBRARY_PATH export LD_LIBRARY_PATH PYTHONPATH=bin/gcc-4.1.2/release/address-model-64 export PYTHONPATH "/users/aa7/Python_m64/bin/python2.6" "/users/aa7/bin" "test.py" > "bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext.output" 2>&1 status=$? echo >> "bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext.output" echo EXIT STATUS: $status >> "bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext.output" if test $status -eq 0 ; then cp "bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext.output" "bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext" fi verbose=1 if test $status -ne 0 ; then verbose=1 fi if test $verbose -eq 1 ; then echo ====== BEGIN OUTPUT ====== cat "bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext.output" echo ====== END OUTPUT ====== fi exit $status ...failed capture-output bin/test_ext.test/gcc-4.1.2/release/address-model-64/test_ext... ...failed updating 1 target... ...skipped 1 target... ...updated 147 targets...

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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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