Mailman 3 August 2009 - 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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Getting object for PyObject (reference counting)
by Murray Cumming Feb. 11, 2010

Feb. 11, 2010

I can't find any definitive documentation that tells me how I should get a boost::python::object to wrap an existing PyObject*. I guess that there's a way to do it that uses an existing reference, and a way that takes an extra reference. -- murrayc(a)murrayc.com www.murrayc.com www.openismus.com

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Fw: g++ compiler limitations other than -ftemplate-depth-n and -DBOOST_PYTHON_MAX_ARITY ?
by Christopher A Mejia Sept. 20, 2009

Sept. 20, 2009

Stefan / cplusplus-sig, Based on Stefan's encouragement, I developed a minimal complete test case exhibiting this problem, contained in the attached files. The compilation command I used was: g++ -DBOOST_PYTHON_MAX_ARITY=40 -I/data/cmejia/install/boost_1_39_0 -I/data/include/python2.6 -c -o foo.o foo.cpp As I explained earlier in the first message of this thread, this fails to compile, but if I remove one double argument towards the end (i.e. edit out one line of foo.hpp and two lines of foo.cpp) it does compile successfully. I would appreciate any further insight into this problem, and hopefully we can use this test case to make Boost.Python an even better tool. Thanks in advance, --Chris P.S. Unfortunately, I was unable to include preprocessed source from "g++ ... -E foo.cpp" because the result was too large for the mailing list system. Christopher A Mejia wrote: > Stefan, > > Thanks for your response. The API that I am trying to wrap is the > Data Client Server portion of the U.S. Naval Research Labs' SIMDIS > Analysis & Display Tool (simdis.nrl.navy.mil). This is free software, > but does require registration and there is a human in the loop of the > approval process. Anyway, I don't feel comfortable redistributing the > software (or preprocessed details), but if you're really interested > you could obtain it directly yourself. Sorry, I'm not interested enough to register at this time. :-) I merely tried to be helpful in debugging the issue. > Apparently this API is a good test case for pushing some of the limits > of Boost.Python. Since you agree that this is probably a compiler > issue, it's unlikely that you or anyone else would be able to > reproduce the same errors anyway. The only compiler issue I mentioned was a misleading error message. I still believe the real issue might be inside boost.python (where some code may not support your high arity, and can't be configured with BOOST_PYTHON_MAX_ARITY), but I lack details to be able to confirm this. > I came up with a workaround, which is to wrap a version of the > function without the last three arguments, i.e. from Python I am OK > with always having those last three parameters set to their default > values. But if anyone has any other ideas to try, I'd like to hear them. It would really be best to construct the proverbial "minimal complete test case" that allows others to reproduce the issue. You may consider writing some stand-alone test using similar calls as in your code, which you then may freely send do this list, or file as an issue to the boost tracker. Regards, Stefan -- ...ich hab' noch einen Koffer in Berlin... _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig(a)python.org http://mail.python.org/mailman/listinfo/cplusplus-sig The following line is added for your protection and will be used for analysis if this message is reported as spam: (Raytheon Analysis: IP=82.94.164.166; e-from=cplusplus-sig-bounces+camejia=raytheon.com(a)python.org; from=seefeld(a)sympatico.ca; date=Jun 8, 2009 2:39:33 PM; subject=Re: [C++-sig] g++ compiler limitations other than -ftemplate-depth-n and -DBOOST_PYTHON_MAX_ARITY ?)

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Trouble optimizing Boost.python integration
by Dan Sanduleac Sept. 8, 2009

Sept. 8, 2009

Hi, I'm trying to compare different python-C wrapping techniques to see which would be faster and also more suited to game development. I'm using Stackless Python 2.6.2 and boost 1.39.0. I implemented a simple Vec3 (3D vector) class in C++ and wrapped it with boost:python. All it does is multiplications and additions, so it implements just two operators. The thing is, it proves to be kind of slow compared to Cython/Pyrex code that does the same. I think it should run faster than Cython code. (Note: Cython is not an abbreviation for C/Python API) I compiled the python library from boost, in release mode, and then linked the vec3 module, provided below, to the compiled boost_python library. (I used -O2 when compiling the vec3 module) The testing goes like this: each "tick", 10000 objects update their position, according to their velocity and timedelta since last "tick", and I'm measuring the average time a tick takes to complete. On my machine doing this with Cython takes ~0.026 sec/tick, while doing it with boost.python takes like 0.052 sec/tick (The overhead introduced by python's iterating through the list of objects each tick is about 0.01 sec) During one tick, for each object, python runs this: "self.position += self.velocity * time_delta", where position and velocity are instances of Vec3. I was hoping for results better than with Cython, by using Boost. Am I doing something wrong? Source code: vec3.cpp ========== #include <boost/python.hpp> using namespace boost::python; class Vec3 { float x, y, z; public: Vec3(float x, float y, float z); Vec3 &operator*=(float scalar); Vec3 operator*(float scalar) const; Vec3 &operator+=(const Vec3 &who); // that `const Vec3` is REALLY needed, unless you want error monsoon to come down }; // === boost:python wrapper === // publish just += and * to python BOOST_PYTHON_MODULE(vec3) { class_<Vec3>("Vec3", init<float, float, float>()) .def(self += self) .def(self * float()) ; } // === implementation === Vec3::Vec3(float x, float y, float z) { this->x = x; this->y = y; this->z = z; } Vec3 & Vec3::operator*=(float scalar) { this->x *= scalar; this->y *= scalar; thiz->z *= scalar;a } Vec3 Vec3::operator*(float scalar) const { return Vec3(*this) *= scalar; } Vec3 & Vec3::operator+=(const Vec3 &who) { this->x += who.x; this->y += who.y; this->z += who.z; return *this; }

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python extended object to native c++ pointer
by Mark Chandler Sept. 2, 2009

Sept. 2, 2009

Im toying around with the idea to use python as an embedded scripting language for a project im working on and have got most things working. However i cant seem to be able to convert a python extended object back into a native c++ pointer. So this is my class: class CGEGameModeBase { public: virtual void FunctionCall()=0; virtual const char* StringReturn()=0; }; class CGEPYGameMode : public CGEGameModeBase, public boost::python::wrapper<CGEPYGameMode> { public: virtual void FunctionCall() { if (override f = this->get_override("FunctionCall")) f(); } virtual const char* StringReturn() { if (override f = this->get_override("StringReturn")) return f(); return "FAILED TO CALL"; } }; Boost wrapping: BOOST_PYTHON_MODULE(GEGameMode) { class_<CGEGameModeBase, boost::noncopyable>("CGEGameModeBase", no_init); class_<CGEPYGameMode, bases<CGEGameModeBase> >("CGEPYGameMode", no_init) .def("FunctionCall", &CGEPYGameMode::FunctionCall) .def("StringReturn", &CGEPYGameMode::StringReturn); } and the python code: import GEGameMode def Ident(): return "Alpha" def NewGamePlay(): return "NewAlpha" def NewAlpha(): import GEGameMode import GEUtil class Alpha(GEGameMode.CGEPYGameMode): def __init__(self): print "Made new Alpha!" def FunctionCall(self): GEUtil.Msg("This is function test Alpha!") def StringReturn(self): return "This is return test Alpha!" return Alpha() Now i can call the first to functions fine by doing this: const char* ident = extract< const char* >( GetLocalDict()["Ident"]() ); const char* newgameplay = extract< const char* >( GetLocalDict()["NewGamePlay"]() ); printf("Loading Script: %s\n", ident); CGEPYGameMode* m_pGameMode = extract< CGEPYGameMode* >( GetLocalDict()[newgameplay]() ); However when i try and convert the Alpha class back to its base class (last line above) i get an boost error: TypeError: No registered converter was able to extract a C++ pointer to type class CGEPYGameMode from this Python object of type Alpha I have done alot of searching on the net but cant work out how to convert the Alpha object into its base class pointer. I could leave it as an object but rather have it as a pointer so some non python aware code can use it. Any ideas? Better Formatted version: http://stackoverflow.com/questions/1355187/python-object-to-native-c-pointer

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[py++] AttributeError: 'Boost.Python.StaticProperty' object attribute '__doc__' is read-only
by Vaclav Smilauer Aug. 31, 2009

Aug. 31, 2009

Hi everybody, I have a small wrapper for a few geometry classes generated; it works on boost 1.34--1.37. I tried to compile and run on boost 1.39 (Boost::python doesn't seem to be mentioned in changelogs for 1.38 or 1.39 though) and I am getting this error: Traceback (most recent call last): File "debian/yade-bzr1703-dbg/usr/lib/yade-bzr1703-dbg/gui/PythonUI_rc.py", line 11, in <module> from miniWm3Wrap import * AttributeError: 'Boost.Python.StaticProperty' object attribute '__doc__' is read-only I only googled the same error at http://de.pastebin.ca/1535109 (which concerns pySide), but no solution. What am I doing wrong? Thanks, Vaclav

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use of hash to map c++ pointers with python objects
by Renato Araujo Aug. 28, 2009

Aug. 28, 2009

Hi all, I'm working on PySide[1] and we have a problem with map between c++ pointers and PyObject. In this section of FAQ: http://www.boost.org/doc/libs/1_40_0/libs/python/doc/v2/faq.html#xref, they give some examples on how to handle this kind of problem. But the point is: dynamic_cast does not work between shared libraries. My wrapper class is not visible to another library then the dynamic_cast fails. Then I tried implement a hash table to map c++ pointers and python objects, but in some point of the code I received the pointer in another class representation and this moves the pointer address to another region of memory, causing a mess in my hash. I would like to know if someone has any idea about how to solve this problem. How can I map a c++ pointer to a PyObject between libraries without use dynamic_cast. I have attached a small use case for this case. Renato Araujo Oliveira Filho [1] PySide = http://pyside.org

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why am I getting a Boost.Python.ArgumentError?
by Tom Haynes Aug. 25, 2009

Aug. 25, 2009

When trying to called a wrapped method (getName) from python, I get the following error: return self.geometry.getName() Boost.Python.ArgumentError: Python argument types in Geometry.getName(Geometry) did not match C++ signature: getName(gfx::Geometry {lvalue}) I don't understand why these don't match, though. It seems to say that the C++ signature is Geometry::getName() (which is true) ... and that's how I'm calling it from python. If I "print self.geometry" I get that it is a gfx.Geometry object. Thanks for your help. -tom

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