Mailman 3 April 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. 6, 2011

Aug. 6, 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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help on abstract class export
by zeb April 29, 2011

April 29, 2011

Hi, I'm trying to export the following code to python, but failed. Please help me! Here is the code: -------------- c++ code: -------------- class IWorker { public: virtual int getData() = 0; }; class Worker : public IWorker { public: int getData() { return 100; } }; extern "C" { IWorker* createWorker(); } -------------- py++ code: -------------- mb.free_fun('createWorker').call_policies = call_policies.return_value_policy(call_policies.return_pointee_value) -------------- In python: -------------- >>> w = createWorker() I got 'TypeError: No to_python (by-value) converter found for C++ type: class IWorker I found that if the IWorker class is not abstract, for example: class IWorker { public: virtual int getData() { return 0; } }; Python doesn't report that error, but the result of the following code is not expected(I think it should be 100). >>> w = createWorker() >>> w.getData() 0 How to solve this problem? Please give some advise. THANK YOU. -- View this message in context: http://boost.2283326.n4.nabble.com/help-on-abstract-class-export-tp3483090p… Sent from the Python - c++-sig mailing list archive at Nabble.com.

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group meeting today
by James Amundson April 21, 2011

April 21, 2011

Today we will have another technical group meeting. Alex and I will discuss approaches to canonical transformations and Lorentz boosts in space charge calculations. --Jim

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inspect module and Boost.Python.function
by Jean Felder April 21, 2011

April 21, 2011

Hi all, I would like to get a list of the arguments of some Boost Python functions in a python program. So, I was thinking of using the inspect module and the getargspec function. However, I get an error: "arg is not a Python function". I'm using python 2.6 and boost python 1.42. Is it possible to combine inspect and boost python function ? Is there a way to get the arguments of a Boost Python function in a python program ? Thanks, Jean Felder

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C++ chain method works unexpectedly in Python
by Charles Solar April 18, 2011

April 18, 2011

I have a python module written in C++, and the C++ code has a few instances that involve method chaining. I was experimenting with python support for these methods and I found something odd. However it seems this is more a python eccentricity than Boost Python, consider the following code sample. class Test(): def __init__( self ): print "Init" def __del__( self ): print "Del" def foo( self ): print "Foo" return self def bar( self ): print "Bar" return self And some sample uses: >> Test().foo().bar() Init Foo Bar <__main__.Test instance at 0x2aef40e33998> >> Note that __del__ was never called, the object still exists somewhere.. There is another odd thing though, if I repeat the same line, the previous version gets destroyed and replaced by the new version, but only after the chain methods are done, eg: >>> Test().foo().bar() Init Foo Bar Del <-- Old one, NOT the current instance <__main__.Test instance at 0x2b72bc78d998> >> However if I do: def Tester(): Test().foo().bar() # To make sure del is not called by the function returning while True: pass >> Tester() Init Foo Bar Del Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 4, in Tester KeyboardInterrupt >> That time __del__ was called immediately ( as intended ). Is there something I should be aware of here? Some sort of difference between the global instances and ones defined in a function? Can I do anything so global instances are cleaned up immediately like they are inside functions? Thanks

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Re: [C++-sig] Avoiding implicit boost::python::extract<> conversions
by Ralf W. Grosse-Kunstleve April 7, 2011

April 7, 2011

If you add the undocumented (sorry) define -DBOOST_PYTHON_BOOL_INT_STRICT Boost.Python will not convert bool to int and vice versa. I have been working with this define for a couple years now with a good experience. (The main reason for the define to be undocumented is that the tests need to be adjusted, which I never found the time for.) ----- Original Message ----- > From:Murray Cumming <murrayc(a)murrayc.com> > To:cplusplus-sig@python.org > Cc: > Sent:Thursday, April 7, 2011 7:02 AM > Subject:[C++-sig] Avoiding implicit boost::python::extract<> conversions > > It looks like boost::python::extract<bool>::check() will happily succeed > on an int python object, and boost::python::extract<int>::check() will > likewise succeed on a bool python object. > > Is there an easy way to discover the actual python type so I can really > get the data I want in the correct type? > > -- > murrayc(a)murrayc.com > www.murrayc.com > www.openismus.com > > _______________________________________________ > Cplusplus-sig mailing list > Cplusplus-sig(a)python.org > http://mail.python.org/mailman/listinfo/cplusplus-sig

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Avoiding implicit boost::python::extract<> conversions
by Murray Cumming April 7, 2011

April 7, 2011

It looks like boost::python::extract<bool>::check() will happily succeed on an int python object, and boost::python::extract<int>::check() will likewise succeed on a bool python object. Is there an easy way to discover the actual python type so I can really get the data I want in the correct type? -- murrayc(a)murrayc.com www.murrayc.com www.openismus.com

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