Mailman 3 March 2007 - Cplusplus-sig

Indexing Suite V2
by Roman Yakovenko March 19, 2007

March 19, 2007

Good evening. Boost.Python library, out of the box, provides support for std::map and std::vector containers. 3 years ago Raoul Gough created new indexing suite, which supports almost all C++ containers. Few month ago I started to use it and found few bugs and missing functionality. The found bugs were fixed and functionality was added. Last year there were 2 discussion on this subject: http://mail.python.org/pipermail/c++-sig/2006-June/010830.html http://mail.python.org/pipermail/c++-sig/2006-June/010835.html >From my experience the indexes suites can peacefully coexist within a project. You can use only one of them, but still it is possible to compile both of them. The new indexing suite was built and tested on Windows( MSVC 7.1 ), Linux( gcc 4.1 ) and MAC. It was reported that it works on other gcc versions too. New indexing suite allowed me to create new and pretty useful call policy - return_range( http://language-binding.net/pyplusplus/documentation/functions/call_policie…) I will be glad to contribute it to the library. Now the question: is it possible to add new indexing suite to the library? This step will simplify the installation process. Thanks. -- Roman Yakovenko C++ Python language binding http://www.language-binding.net/

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How to do inheritance in boost.python?
by michael kapelko March 18, 2007

March 18, 2007

I have this: #include <boost/python.hpp> #include <iostream> using namespace boost::python; using namespace std; class Base { public: virtual ~Base() { } virtual int f() = 0; }; class BaseWrap: public Base, public wrapper<Base> { public: int f() { return this->get_override("f")(); } }; BOOST_PYTHON_MODULE(hello) { class_<BaseWrap, boost::noncopyable>("Base") .def("f", pure_virtual(&Base::f)) ; } Module compiles ok into hello.so. But then I do in Python: >>> import hello >>> base = Base(); Traceback (most recent call last): File "<stdin>", line 1, in ? NameError: name 'Base' is not defined >>> class Derived(Base): ... def f(self): ... return 42; ... Traceback (most recent call last): File "<stdin>", line 1, in ? NameError: name 'Base' is not defined What's wrong with the code? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Also, here's a code with not pure virtual func: #include <boost/python.hpp> #include <iostream> using namespace boost::python; using namespace std; class Base { public: virtual ~Base() { } virtual int f() { return 0; } }; class BaseWrap: public Base, public wrapper<Base> { public: int f() { if (override f = this->get_override("f")) return f(); return Base::f(); } int default_f() { return this->Base::f(); } }; BOOST_PYTHON_MODULE(hello) { class_<BaseWrap, boost::noncopyable>("Base") .def("f", &Base::f, &BaseWrap::default_f) ; } And in Python I get the same error that Base isn't defined. Thanks.

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building boost_python with mingw in eclipse
by Luca Sbardella March 18, 2007

March 18, 2007

Basically, I get a lots of 'undefined reference to _imp__'. This seems a problem connected with the handling of __dllimport/__dllexport. Do I need to include an extra flag in the Preprocessor stage (for the debug build I currently use _DEBUG, BOOST_PYTHON_DYNAMIC_LIB and BOOST_PYTHON_SOURCE). Or anything else I need to check ? Best Regards Luca

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virtual method issue ?
by Adrien Saladin March 17, 2007

March 17, 2007

Dear all, I'm exposing a C++ library to python using boost python. Almost everything works fine except this: I have a Minimizer class that needs a "function" object to minimize. These objects communicates with std::vector<double> and I think the problem is around there... I had to (partially) expose std::vector<double> to python because of a lvalue convertor problem. The function object is derived from an abstract class "Base". When I try to redefine the function in python, the std::vector doesn't seem to be correctly transmitted between objects. You will find bellow the minimal example I found to reproduce the undesired feature... Any advice would be really appreciated ! Thanks, Adrien ============ C++ CODE =============== #include <boost/python.hpp> #include <boost/python/module.hpp> #include <boost/python/class.hpp> #include <boost/python/wrapper.hpp> #include <boost/python/call.hpp> #include <boost/python/suite/indexing/indexing_suite.hpp> #include <boost/python/suite/indexing/vector_indexing_suite.hpp> #include <iostream> #include <vector> #include <cassert> typedef std::vector<double> Vdouble; using namespace boost::python; struct Base { virtual ~Base(){}; virtual double Function(const Vdouble& X, Vdouble& Grad)=0; }; struct BaseWrap: Base, wrapper<Base> { double Function(const Vdouble& v, Vdouble& Grad) { return this->get_override("Function")(v,Grad); } }; struct Minimizer { Minimizer(Base& base):_base(base) { _vec.resize(5); _Grad.resize(5); for (uint i=0; i<5; i++) {_vec[i]=0.0; _Grad[i]=0.0;} }; void minimize(){ _base.Function(_vec, _Grad); std::cout << "_Grad[0] =" << _Grad[0] << std::endl; assert(_Grad[0]>=5.0); } //Data: Base& _base; Vdouble _vec; Vdouble _Grad; }; struct Derived: public Base { double Function(const Vdouble& v, Vdouble& grad) { grad[0]=12; return v[0]; } }; using namespace boost::python; BOOST_PYTHON_MODULE(minim) { class_<std::vector<double> >("std_vector_double") .def(vector_indexing_suite<std::vector<double> >()) ; class_<BaseWrap, boost::noncopyable>("Base") .def("Function",pure_virtual(&Base::Function)); class_<Derived, bases<Base> >("Derived") .def("Function",&Derived::Function ); class_<Minimizer>("Minimizer", init< Base& >() ) .def("minimize", &Minimizer::minimize); } ========== END C++ CODE ======== compilation: g++ -o minim.so -shared minim.cpp -I/usr/include/python2.4 -lboost_python -lpython2.4 ========== PYTHON CODE: ========= from minim import * class PyDerived(Base): def Function(self, v, grad): grad[0]=45.0 return 0 pyderived=PyDerived() v=std_vector_double() grad=std_vector_double() for i in range(5): v.append(0.0) grad.append(0.0) derived=Derived() minim=Minimizer(derived) minim.minimize() #this one is OK assert grad[0]>5.0, "grad[0]>5.0" #this one is OK pyderived.Function(v,grad) print grad[0] assert grad[0]==45.0, "grad[0]==45.0" #this one is OK minim=Minimizer(pyderived) minim.minimize() # <--- Here I get a C++ assert error (not OK...) =========== END PYTHON CODE ==================

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building boost_python with mingw in eclipse
by Luca Sbardella March 17, 2007

March 17, 2007

Hi all, I'm C++ programmer looking to port my libraries into python. After some time I decided to go with boost_python template wrapping approach. I need to build the application under windows and I would like to use eclipse for the job combines with the mingw compiler. Compilation works fine but it just won't link. Do anybody know what flags I need to use in the compiler or linker to make this work? I successfully complied boost_python using visual studio and bjam but I would like to get this working in eclipse with mingw. In eclipse I use for make the mingw32-make.exe, extra compiler flags BOOST_PYTHON_DYNAMIC_LIB and BOOST_PYTHON_SOURCE and the python library directory is included in the path (needless to say the boost and python include directories are also included). Any help would be appreciated. Luca

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std::tr1::shared_ptr and C++ Singletons
by Piotr Jaroszynski March 16, 2007

March 16, 2007

Hello, I have 2 problems: 1) class_<Foo, std::tr1::shared_ptr<Foo> > doesn't work=compile errors while boost::shared_ptr does. In the code I am writing bindings for std::tr1::shared_ptr is used. 2) I am not sure how to handle C++ Singletons. I thought that the proper way is to use return_value_policy<reference_existing_object>() for functions returning pointers to them as described in [1], but at the bottom of [2] Dave seems to disagree or I am missing something. Btw. how would you handle the situation when the get_it() is a method of object you want to get? I used: def("get_it", &Foo::get_instance, return_value_policy<reference_existing_object>()); Is it the best solution? [1] - http://www.boost.org/libs/python/doc/v2/reference_existing_object.html [2] - http://mail.python.org/pipermail/c++-sig/2005-January/008481.html -- Best Regards, Piotr Jaroszynski

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Create sub-module
by John Reid March 16, 2007

March 16, 2007

Hi, Is it possible to create a sub-module inside a boost.python created module? At the moment I am using separate DLLs for this. I had a look at the documentation for scope and didn't find anything. I did find this old post: http://mail.python.org/pipermail/c++-sig/2002-June/001297.html Is the recommended way to use separate DLLs? John.

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Rhetorics of Hypertext
by hypertextual＠phonereader.com March 13, 2007

March 13, 2007

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Re: [C++-sig] Boost python and import error
by Ralf W. Grosse-Kunstleve March 13, 2007

March 13, 2007

> :-). Can you post your scons script? Thank you There are two SConscripts which need a few supporting Python scripts. It is all part of the source bundles here: http://cci.lbl.gov/cctbx_build/all.html There are two approaches: 1. perl cctbx_python_25_bundle.selfx Capture the compile and link commands from the output and throw away everything else. Configure your own build system to spit out the same commands. The only complication is under Mac OS X, where a helper script is used: libtbx/libtbx/command_line/mac_os_x_ld_bpl_dll.csh 2. Use libtbx/SConscript boost_adaptbx/SConscript as a starting point for your own SConscipt. Copy some supporting Python code from the libtbx tree as needed. Everything is also under CVS: http://cctbx.cvs.sourceforge.net/cctbx/ Ralf ____________________________________________________________________________________ Don't get soaked. Take a quick peek at the forecast with the Yahoo! Search weather shortcut. http://tools.search.yahoo.com/shortcuts/#loc_weather

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Re: [C++-sig] Boost python and import error
by Ralf W. Grosse-Kunstleve March 12, 2007

March 12, 2007

> No. It is important to compile Boost.Python shared library with bjam, > but after this you can switch to your favorite build system. You can build the boost_python runtime with any build system you like. E.g. I have been using scons for years. You just have to get the compile & link commands right. In the past there was a way to get bjam (version 1) show the commands it was issuing, I think it was -d2. I guess something similar if not the same should also work with the current bjam. Ralf ____________________________________________________________________________________ Sucker-punch spam with award-winning protection. Try the free Yahoo! Mail Beta. http://advision.webevents.yahoo.com/mailbeta/features_spam.html

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