Mailman 3 December 2007 - Cplusplus-sig

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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Base class defined in other header file not included in bp::bases<>
by Haridev, Meghana Sept. 14, 2008

Sept. 14, 2008

Hi Folks, I'm having some trouble generating boost-python wrapper code using pyplusplus for a derived class which has one of its base classes defined in another file. Simple scenario: mydir/ other.hpp: class baseB{ }; hierarchy.hpp: #include "other.hpp" class baseA{ }; class derivedC: public baseA, public baseB{ }; generate_code.py: import os from pyplusplus import module_builder mb = module_builder.module_builder_t( files=['hierarchy.hpp'] ) mb.build_code_creator( module_name='inherit' ) mb.code_creator.user_defined_directories.append( os.path.abspath('.') ) mb.write_module('boost_hierarchy.cpp') ------------------------------------------------------------------------ ------------------------------------------------- Generated code (boost_hierarchy.cpp) looks like this: // This file has been generated by pyplusplus. #include "boost/python.hpp" #include "hierarchy.hpp" namespace bp = boost::python; BOOST_PYTHON_MODULE(inherit){ bp::class_< baseA >( "baseA" ); bp::class_< derivedC, bp::bases< baseA > >( "derivedC" ); } How can I get pyplusplus to add 'baseB' to bp::bases<> for 'derivedC' class when 'baseB' class is defined in another file (present in the same directory or different directory)? When I move the definition of 'baseB' class to hierarchy.hpp, boost wrapper for 'derivedC' is correctly generated as: bp::class_< derivedC, bp::bases< baseA, baseB > >( "derivedC" ); Thanks, -Meghana.

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ANNOUNCE: PyBindGen 0.8
by Gustavo Carneiro June 3, 2008

June 3, 2008

The other day I released PyBindGen 0.8. Main news is that it features a new experimental header file scanner based on pygccxml (i.e., it's similar to py++ in scope, if not in maturity, but does not use boost.pythonunderneath). == What == PyBindGen is a Python module that is geared to generating C/C++ code that binds a C/C++ library for Python. It does so without extensive use of either C++ templates or C pre-processor macros. It has modular handling of C/C++ types, and can be easily extended with Python plugins. The generated code is almost as clean as what a human programmer would write, and does not depend on any library or header files besides Python itself. == Where == https://launchpad.net/pybindgen/ == NEWS == - Support C++ instance attributes through getter/setter methods - Support functions as methods of C++ classes - Support the PyObject* type - Support unsigned int, C strings (char*) (from Mark Lee) - Add basic support for enum types - New experimental automatic module generator based on C/C++ header file scanner and annotations in comments, using pygccxml - Some bug fixes -- Gustavo J. A. M. Carneiro INESC Porto, Telecommunications and Multimedia Unit "The universe is always one step beyond logic." -- Frank Herbert

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Raoul Gough's container suite with svn boost-trunk boost.python?
by John Reid May 18, 2008

May 18, 2008

Has anyone tried using Raoul's container suite with the svn boost-trunk? I'm getting the following error: C:\Dev\ThirdParty\boost\boost-trunk\boost/python/detail/caller.hpp(236) : error C2903: 'extract_return_type' : symbol is neither a class template nor a function template C:\Dev\ThirdParty\boost\boost-trunk\boost/python/detail/caller.hpp(232) : while compiling class template member function 'boost::python::detail::py_func_sig_info boost::python::detail::caller_arity<2>::impl<F,Policies,Sig>::signature(void)' with [ F=boost::python::list (__cdecl *)(std::vector<biopsy::binding_hit> &,boost::python::indexing::slice), Policies=boost::python::indexing::detail::postcall_override<boost::python::indexing::default_container_policies>, Sig=boost::mpl::vector3<boost::python::list,std::vector<biopsy::binding_hit> &,boost::python::indexing::slice> ] So the problem seems to be there is no extract_return_type in boost::python::indexing::detail::postcall_override<boost::python::indexing::default_container_policies> If I remember correctly, I've installed Roman's version by copying it into boost/python/suite/indexing John.

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'iteritems', 'iterkeys' and 'itervalues' in dict
by Nindi Singh April 11, 2008

April 11, 2008

Apolgies for not putting the subject line in my last email. In the Boost.Python dict class there are methods 'iteritems', 'iterkeys' and 'itervalues' all returning objects. How exactly are you supposed to use these objects (iterators) ? ___________________________________________________________ Inbox full of spam? Get leading spam protection and 1GB storage with All New Yahoo! Mail. http://uk.docs.yahoo.com/nowyoucan.html

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Custom smart pointer with same behaviour as shared_ptr
by Francis Moreau Jan. 23, 2008

Jan. 23, 2008

Hi, I am passing Python objects to C++ through a shared_ptr smart pointer and it's work well. However I need to have the same behaviour as shared_ptr but with my own version of smart pointer. I try to register and expose my custom smart pointer but I have this compilation error: boost/python/pointee.hpp(28) : error C2039: 'element_type': is not a member of 'CountedObjPtr<T>' with [ T=PyCallEngineState ] boost/python/pointee.hpp(38) : see reference to class template instantiation 'boost::python::detail::pointee_impl<false>::apply<T>' being compiled with [ T=CountedObjPtr<PyCallEngineState> ] boost/python/register_ptr_to_python.hpp(17) : see reference to class template instantiation 'boost::python::pointee<T>' being compiled with [ T=CountedObjPtr<PyCallEngineState> ] PythonModules.cpp(113) : see reference to function template instantiation 'void boost::python::register_ptr_to_python<CountedObjPtr<T>>(void)'being compiled with [ T=PyCallEngineState ] Here is the content of the from_python file for my smart pointer: template <class T> struct CountedObjPtr_from_python { CountedObjPtr_from_python() { converter::registry::insert(&convertible, &construct, type_id<CountedObjPtr<T> >()); } static void* convertible(PyObject* p) { if (p == Py_None) { return p; } return converter::get_lvalue_from_python( p, python::converter::registered<T>::converters); } static void construct(PyObject* source, python::converter::rvalue_from_python_stage1_data* data) { void* const storage = ((python::converter::rvalue_from_python_storage<CountedObjPtr<T> >*)data)->storage.bytes; // Deal with the "None" case. if (data->convertible == source) { new (storage) CountedObjPtr<T>(); } else { new (storage) CountedObjPtr<T>(static_cast<T*>(data->convertible)); } data->convertible = storage; } }; And here is the code where I register the smart pointer: namespace boost{ namespace python{ template <class T> struct pointee< CountedObjPtr<const T> > { typedef T type; }; template <class T> inline T* get_pointer(CountedObjPtr<const T> const& p) { return const_cast<T*>(p.get()); } }} template <typename T> void register_CountedObjPtr_conversions() { boost::python::converter::registry::insert( &CountedObjPtr_from_python<T>::convertible, &CountedObjPtr_from_python<T>::construct, boost::python::type_id<CountedObjPtr<T> >()); } BOOST_PYTHON_MODULE(CallEngineExtending) { python::class_<PyCallEngineState, PyCallEngineState_Wrapped, boost::noncopyable>("PyCallEngineState") ; //register_ptr_to_python<boost::shared_ptr<PyCallEngineState> >(); python::register_ptr_to_python<CountedObjPtr<PyCallEngineState> >(); register_CountedObjPtr_conversions<PyCallEngineState>(); } Is anyone knows what is missing or wrong with this code? Also, I am not sure this code manages the ref counting properly since there is no call to borrowed or something like this? Any help would be appreciated, Francis

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std::tr1::shared_ptr as boost::shared_ptr
by Piotr Jaroszynski Jan. 16, 2008

Jan. 16, 2008

Hello, I am exposing a C++ app, which makes heavy use of tr1::shared_ptr, which seems to be exactly(?) the same as boost::shared_ptr. I have managed to make most of the stuff work just as it would be boost::shared_ptr ( additionally adding support for shared_ptr<const T> - thanks to [1] ): namespace my_app_namespace { //Make Boost.Python work with std::tr1::shared_ptr<> template<typename T_> inline T_ * get_pointer(std::tr1::shared_ptr<T_> const & p) { return p.get(); } //Make Boost.Python work with std::tr1::shared_ptr<const> template<typename T_> inline T_ * get_pointer(std::tr1::shared_ptr<const T_> const & p) { return const_cast<T_*>(p.get()); } } namespace boost { namespace python { //Make Boost.Python work with std::tr1::shared_ptr<> template<typename T_> struct pointee<std::tr1::shared_ptr<T_> > { typedef T_ type; }; //Make Boost.Python work with std::tr1::shared_ptr<const> template<typename T_> struct pointee<std::tr1::shared_ptr<const T_> > { typedef T_ type; }; } } What is still not working is the implicit conversion of Foo and Derived for functions taking std::tr1::shared_ptr<Foo>. With boost::shared_ptr it just works when you add the bp::bases<Foo> to the Derived: func(boost::shared_ptr<Foo>) ... bp::class_<Foo> ... bp::class_<Derived, bp::bases<Foo> > ... and func can take both Foo and Derived. But with std::tr1::shared_ptr I have to use: func(std::tr1::shared_ptr<Foo>) ... bp::class_<Foo, std::tr1::shared_ptr<Foo> > ... bp::class_<Derived, std::tr1::shared_ptr<Derived>, bp::bases<Foo> > ... bp::implicitly_convertible<std::tr1::shared_ptr<Foo>, std::tr1::shared_ptr<Derived> >(); How can I make it working just as with boost::shared_ptr? Btw. I have seen [2] already, but it doesn't seem to cover that. [1] - http://language-binding.net/pyplusplus/troubleshooting_guide/shared_ptr/sha… [2] - http://language-binding.net/pyplusplus/troubleshooting_guide/smart_ptrs/sma… -- Best Regards, Piotr Jaroszynski

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Re: [C++-sig] [Numpy-discussion] Overloading sqrt(5.5)*myvector
by Bruce Sherwood Jan. 1, 2008

Jan. 1, 2008

I should have added: This structure worked with the older version of VPython which used Numeric, but it doesn't work in the beta version which uses numpy. Since I don't know enough about either numpy or Boost, I'm left guessing which subsystem is the source of my difficulties, and clueless about how to remedy them. Bruce Sherwood Bruce Sherwood wrote: > Thanks for the comment, which limits the range of possible solutions. > The VPython vector class is implemented in C++, not in Python. I made up > the simple test in my previous note to try out the solution that had > been offered and which you have usefully ruled out. Here is the relevant > part of the vector class, which indeed doesn't look like an ndarray: > > inline vector > operator*( const double s) const throw() > { return vector( s*x, s*y, s*z); } > > and here is the free function for right multiplication: > > inline vector > operator*( const double& s, const vector& v) > { return vector( s*v.x, s*v.y, s*v.z); } > > Maybe the unsolvable problem is in the Boost definitions: > > py::class_<vector>("vector", py::init< py::optional<double, double, > double> >()) > .def( self * double()) > .def( double() * self) > > Left multiplication is fine, but right multiplication isn't. > > Bruce Sherwood > > Robert Kern wrote: > >> Bruce Sherwood wrote: >> >> >>> Thanks for the suggestion. It hadn't occurred to me to try to override >>> numpy as you suggest. However, when I try the code shown below as the >>> start of a test of this scheme, I get the following error: >>> >>> Traceback (most recent call last): >>> File "C:\Documents and Settings\Bruce\My >>> Documents\0VPythonWork\vectors.py", line 24, in <module> >>> numpy.float64.__mul__ = new_mul >>> TypeError: can't set attributes of built-in/extension type 'numpy.float64' >>> >>> I'm copying this to the numpy discussion list, as maybe someone there >>> will see where to go starting from your suggestion. >>> >>> >> Like most (or all) builtin-types, the numpy float scalars do not permit >> replacing their methods from Python. >> >> I'm not familiar with vpython's vector. If you can make it "not look like an >> ndarray", then you should be able to just implement __rmul__ on vector. >> >> >> > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion(a)scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion >

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Re: [C++-sig] Exposing C Array members to python using boost
by Carpman, David Dec. 29, 2007

Dec. 29, 2007

> -----Original Message----- > Message: 2 > Date: Sat, 22 Dec 2007 00:00:09 +0200 > From: "Roman Yakovenko" > Subject: Re: [C++-sig] Exposing C Array members to python using boost > To: "Development of Python/C++ integration" <c++-sig(a)python.org> > Message-ID: > <7465b6170712211400p429b0abdg232e24692b407e06(a)mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On Dec 20, 2007 1:41 AM, Carpman, David wrote: > > Here is my situation: I'm trying to wrap some legacy C-structures that > define a network packet structure that will be written by python and read > by some embedded computer. I have no control over the definition of these > structures, nor can I add to or change the header files. My hang-up is > that some of the members in these structures are defined as C-arrays, for > example, int numsamples[32]. I would like to have access in python to the > elements of these arrays for reading and writing. Scalar primitive members > work fine. > > > I would like to avoid having to write C++ wrapper classes for the C- > structs containing the C-arrays, as there are many dozens of them. > > I'd be very thankful if someone could help! > > Take a look on next code: > > http://pygccxml.svn.sourceforge.net/viewvc/pygccxml/pyplusplus_dev/pyplusp > lus/code_repository/array_1.py?revision=1097&view=markup > > search for register_array_1 function. > > You can also to try > Py++(http://language-binding.net/pyplusplus/pyplusplus.html), code > generator for Boost.Python library, it handles such cases > automatically. > > -- > Roman Yakovenko > C++ Python language binding > http://www.language-binding.net/ > Thanks very much for the reply, Roman. I tried Py++ and it indeed automatically handles the case I outlined above concerning C-array members, and with much less tedious writing of registration code. I also found it convenient to use to insert some other C++ code for each of my structures that normally I wrote by hand. The API docs and examples on your webpage were very helpful. Warm regards, David Carpman

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