Mailman 3 January 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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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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Somewhat beginners error in using boost::python::list from C++?
by Michael Wand Jan. 17, 2011

Jan. 17, 2011

Hello, sorry if this question is too trivial, but I've got some rather strange problem with using the boost::python type wrapper for the python list. It goes as follows: I've got a very small demo program (say main.cpp). Running it causes a segfault. (The actual project is much larger, of course.) The system I use is a Linux OpenSuse 11.1, with the distribution package python-2.6.0-2.23.1 installed. I manually installed boost 1.44 (because the newer versions didn't quite work with the boost-log package, which is needed for the actual project). Which other information might be helpful? This is the program: ******************************************* #include <iostream> #include <boost/python.hpp> using namespace std; int main() { boost::python::list myList; myList.append("foo"); myList.append("fork"); cerr << "Printing length of list." << endl; cerr << "Length of myList: " << boost::python::len(myList) << endl; // the above line causes a segfault! cerr << "TheList: " << boost::python::extract<string>(myList[0])() << "," << boost::python::extract<string>(myList[1])() << endl; cerr << "Finished" << endl; } ******************************************* which I compile by the two commands: /usr/bin/c++ -O0 -Wall -g -I. -I/usr/include/python2.6 -I/usr/local/include -o main.o -c main.cpp /usr/bin/c++ -O0 -Wall -g main.o -o boost_list_test -rdynamic -L/usr/local/lib /usr/local/lib/libboost_python.so -lpython2.6 -Wl,-rpath,/usr/local/lib The segfault occurs at the call to boost::python::len(myList). I debugged the program with gdb, but the backtrace #0 0xb7ec6027 in PyErr_Occurred () from /usr/lib/libpython2.6.so.1.0 #1 0x0804b0b1 in main () at main.cpp:15 doesn't really tell me anything. Interestingly, removing the offending line causes a segfault at the *next* line, with a more verbose backtrace: #0 0xb7e529d7 in PyInt_FromLong () from /usr/lib/libpython2.6.so.1.0 #1 0x0804ba33 in arg_to_python (this=0xbfffee70, x=@0xbfffef48) at /usr/local/include/boost/python/converter/builtin_converters.hpp:122 #2 0x0804ba5d in boost::python::api::object_initializer_impl<false, false>::get<int> (x=@0xbfffef48) at /usr/local/include/boost/python/object_core.hpp:393 #3 0x0804ba9e in boost::python::api::object_base_initializer<int> (x=@0xbfffef48) at /usr/local/include/boost/python/object_core.hpp:315 #4 0x0804bab1 in object<int> (this=0xbfffeedc, x=@0xbfffef48) at /usr/local/include/boost/python/object_core.hpp:334 #5 0x0804bae1 in boost::python::api::object_operators<boost::python::api::object>::operator[]<int> (this=0xbfffef28, key=@0xbfffef48) at /usr/local/include/boost/python/object_items.hpp:61 #6 0x0804af46 in main () at main.cpp:17 I really don't understand what I'm doing wrong. Do I need to resize the list before using append? The documentation (http://www.boost.org/doc/libs/1_44_0/libs/python/doc/v2/list.html) doesn't say anything about this. Any tips or hints are greatly appreciated! Thankyou, - Michael Wand

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problem returning polymorphic shared_ptr instances
by Matt Bendiksen Jan. 13, 2011

Jan. 13, 2011

I'm stumped on a problem encountered when trying to return a derived instance via a shared_ptr to python. The python instance is always shown as a base class and not the subclass that was created, as if the instance was sliced. struct A { }; struct B : A { }; shared_ptr<A> get_a_or_b_instance(bool returnB) { return shared_ptr<A>(returnB ? new B() : new A()); } … def("get_a_or_b_instance", get_a_or_b_instance); class_<A, boost::shared_ptr<A> >("A", init<>()) ; class_<B, bases<A>, boost::noncopyable>("B", init<>()) ; And the Python result is always a type A object: >>> type(app.get_a_or_b_instance(False)) <class 'app.A'> >>> type(app.get_a_or_b_instance(True)) <class 'app.A'> Where I would expect the derived instance type B returned from the second call. I'm using Boost 1.42.0. Thanks in advance for any help. Matt Bendiksen

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Status of Numpy support in boost python - II
by Neal Becker Jan. 7, 2011

Jan. 7, 2011

I was just re-reading these posts: Status of Numpy support in boost python http://web.archiveorange.com/archive/v/YJlerznoeRShLhlurQzC I wonder if there are any updates? Is ndarray working with current (1.45.0) boost?

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Boost / python-devel / python dependency problem
by David Aldrich Jan. 6, 2011

Jan. 6, 2011

Hi I wonder if someone could help me out with a yum dependency problem please? I am running Centos 5.5. I installed Boost 1.40 from the Black Op Software repo. I now need to install python-devel, but when I do so I get: ================================================================= $ sudo yum install python-devel Loaded plugins: fastestmirror, priorities Loading mirror speeds from cached hostfile * addons: anorien.csc.warwick.ac.uk * base: anorien.csc.warwick.ac.uk * extras: mirror.as29550.net * updates: anorien.csc.warwick.ac.uk 943 packages excluded due to repository priority protections Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package python-devel.i386 0:2.4.3-27.el5 set to be updated --> Processing Dependency: python = 2.4.3-27.el5 for package: python-devel --> Finished Dependency Resolution python-devel-2.4.3-27.el5.i386 from base has depsolving problems --> Missing Dependency: python = 2.4.3-27.el5 is needed by package python-devel-2.4.3-27.el5.i386 (base) Error: Missing Dependency: python = 2.4.3-27.el5 is needed by package python-devel-2.4.3-27.el5.i386 (base) You could try using --skip-broken to work around the problem You could try running: package-cleanup --problems package-cleanup --dupes rpm -Va --nofiles --nodigest The program package-cleanup is found in the yum-utils package. ================================================================= However, I do have python 2.4 installed: ================================================================= $ sudo yum install python Loaded plugins: fastestmirror, priorities Loading mirror speeds from cached hostfile * addons: anorien.csc.warwick.ac.uk * base: anorien.csc.warwick.ac.uk * extras: mirror.as29550.net * updates: anorien.csc.warwick.ac.uk 943 packages excluded due to repository priority protections Setting up Install Process Package matching python-2.4.3-27.el5.i386 already installed. Checking for update. Nothing to do ================================================================= Finally, this may be useful information: ================================================================= [daldrich@localhost Zodiac]$ yum list python Loaded plugins: fastestmirror, priorities blackop 474/474 943 packages excluded due to repository priority protections Installed Packages python.i386 2.4.3-27.el5_5.3 installed [daldrich@localhost Zodiac]$ ================================================================= So python-devel seems to want python 2.4.3-27.el5 but I have 2.4.3-27.el5_5.3 Any suggestions how I can fix this please? David

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Boost.Python and python 3.x?
by Andrew Ho Jan. 2, 2011

Jan. 2, 2011

Hi, I'm trying to build Boost.Python to use Python 3.1, however I'm getting a bunch of errors (missing functions/members, etc.). I was able to get Boost.Python to compile correctly when using Python 2.6 so I don't think the problem is in my setup. I did a search and as far as I can tell there's no support for python 3.x being built at Boost 1.41, however I haven't found anything for Boost 1.45. There were references to a GSoC project to fix this, did this ever get finished? If so, is there something different between the Python 3.x and Python 2.x jam files that would cause this (other than referencing the correct includes & libs)? Here's my jam file for python 3.1 (C:\Python31 contains the source download of Python 3.1.2, built for Windows x64 release platforms): using msvc ; import os ; using python : 3.1 : # sources C:\\Python31 : # requirements <include>C:\\Python31\\Include <include>C:\\Python31\\PC <library-path>C:\\Python31\\PCBuild\\amd64 ; And I'm compile with this command: bjam link=static threading=multi address-model=64 variant=release toolset=msvc-9.0 -a --with-python

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