Mailman 3 April 2007 - Cplusplus-sig

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.

4 4

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.

3 9

'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

2 1

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

4 13

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

3 5

C++ singleton
by Emmanuel Taurel Oct. 31, 2007

Oct. 31, 2007

Hello everybody, I am actually writing an interface to python for an existing C++ library using Boost. This library has a C++ singleton class. This class has only one constructor (with arguments) which is "protected" because it's a singleton. I am not able to build a Boost interface to this class because the compiler complains that the constructor I have given to Boost in the class_xxx constructor argument is not public (which is true) ! Therefore, my question is simple : How is it possible to interface such a class with only one constructor which is protected and a static method to create/access the object ? Thank's very much for your answer. Sincerely Emmanuel Taurel (etaurel(a)cells.es) PS : By the way, is there a searchable archive of this mailing list ?

4 3

[Boost.Python] inconsistent use of function pointer typedef
by Sebastian Ramacher May 7, 2007

May 7, 2007

I just wanted to repost a patch I've submitted to the SourceForge tracker some days ago. The patch fixes the inconsistent use of the function pointer typedef 'convertible_function' at the declaration and definition of 'boost::python::converter::registry::insert' and 'boost::python::converter::registry::push_back'. The link to the SoruceForge tracker item is: https://sourceforge.net/tracker/?func=detail&atid=307586&aid=1707377&group_… Regards, Sebastian Ramacher Index: boost/python/converter/registry.hpp =================================================================== RCS file: /cvsroot/boost/boost/boost/python/converter/registry.hpp,v retrieving revision 1.18 diff -u -r1.18 registry.hpp --- boost/python/converter/registry.hpp 16 May 2005 03:30:56 -0000 1.18 +++ boost/python/converter/registry.hpp 25 Apr 2007 12:24:56 -0000 @@ -30,7 +30,7 @@ BOOST_PYTHON_DECL void insert(to_python_function_t, type_info); // Insert an lvalue from_python converter - BOOST_PYTHON_DECL void insert(void* (*convert)(PyObject*), type_info); + BOOST_PYTHON_DECL void insert(convertible_function, type_info); // Insert an rvalue from_python converter BOOST_PYTHON_DECL void insert( Index: libs/python/src/converter/registry.cpp =================================================================== RCS file: /cvsroot/boost/boost/libs/python/src/converter/registry.cpp,v retrieving revision 1.30 diff -u -r1.30 registry.cpp --- libs/python/src/converter/registry.cpp 16 Sep 2006 18:43:53 -0000 1.30 +++ libs/python/src/converter/registry.cpp 25 Apr 2007 12:24:06 -0000 @@ -208,7 +208,7 @@ } // Insert an rvalue from_python converter - void insert(void* (*convertible)(PyObject*) + void insert(convertible_function convertible , constructor_function construct , type_info key) { @@ -224,7 +224,7 @@ } // Insert an rvalue from_python converter - void push_back(void* (*convertible)(PyObject*) + void push_back(convertible_function convertible , constructor_function construct , type_info key) {

2 3

Problem exposing container iterator with boost::iterator_adaptor
by Mitch Jones May 2, 2007

May 2, 2007

I've been experimenting with the boost::python library and slowly getting the hang of it, although I've run into a problem I don't quite understand. I have a container class that provides begin and end functions that are implemented with the help of boost::iterator_adaptor. The iterator is forward only. This class and the thing it contains is then exported to python via boost::python. A snippet of the definitions I have: class_<BaseWidget, shared_ptr<BaseWidget> >("BaseWidget", no_init) .def("__repr__", &Widget::name); class_<BigWidget, bases<BaseWidget>("BigWidget", no_init); class_<LittleWidget, bases<BaseWidget>(" LittleWidget", no_init); class_<vector<Widget> >("Widgets", no_init) .def(vector_indexing_suite<vector<Widget>, true>()); class_<WidgetContainer, shared_ptr<WidgetContainer>, noncopyable >(" WidgetContainer", no_init) .def("__iter__", range(&Container::begin, &Container::end) //the iterator returns shared_ptr<Widget> .def("contents", &WidgetContainer::contents); //returns vector<Widget> When used in python, I get a "pure virtual method called" error followed by a terminate/abort when I try to iterate over WidgetContainer. widgets = container_factory() # factory that supplies a WidgetContainer for some_widget in widgets : print some_widget If I ignore iteration and instead return a list, I have no problem: for some_widget in widgets.contents(): print some_widget Is there some more scaffolding I still need to define to support iteration? It's not really clear to me what the error really means. The Widget base class has no virtual functions other than it's destructor. Is it referring to the iterator_adaptor? Does the iterator_adaptor class need to be exposed to python? Is the iterator_adaptor a red herring and the real issue in Widget and its descendants and I've missed something obvious? -- Mitch Jones mitch(a)niftyneato.com

2 2

Re: [C++-sig] Need strategic advice designing Boost/Python program
by Ralf W. Grosse-Kunstleve April 30, 2007

April 30, 2007

> This, together with your point further down that you want to add python > methods that are only ever used inside python make it sound as if > a C++ base class derived from in python may be the best approach. FWIW: there is a very powerful alternative to this: injecting. For example: class _histogram(boost.python.injector, ext.histogram): def show(self, f=None, prefix="", format_cutoffs="%.8g"): if (f is None): f = sys.stdout fmt = "%s" + format_cutoffs + " - " + format_cutoffs + ": %d" for info in self.slot_infos(): print >> f, fmt % (prefix, info.low_cutoff, info.high_cutoff, info.n) The boost.python.injector is a small utility class defined in boost_adaptbx (adaptor toolbox), boost/python.py. The difference is that objects of ext.histogram will have the .show() method, even if they are created in C++. I.e. even if you only have a C++ constructor, you can have pure Python methods. To give proper credit: this trick is due to David Abrahams. It was one of the big aha moments in my life when he explained it to me. Ralf P.S.: you can also do it like this: def histogram_show(self, f=None, prefix="", format_cutoffs="%.8g"): # exact same code ext.histogram.show = histogram_show but it doesn't look nearly as nice. You can also make it look nice with decorators if you don't care about Python 2.2 and 2.3 compatibility. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

2 1

Need strategic advice designing Boost/Python program
by Craig Finch April 30, 2007

April 30, 2007

As a fairly new boost.python user, I would like some expert advice on which strategy to use in using Boost and Python, so that I don't go down a dead end. A clean interface is more important to me than efficiency. I am writing a numerical solver. I want most of the code to be in Python for ease of development. However, I want to implement some objects in C++ for speed, because they use iterative solution methods. I envision my Python code as creating a mesh on a domain, calling a C++ solver, and performing post-processing such as plotting. The cleanest way to do this seems to be to create a complex "mesh" object in Python, and then pass all the mesh data to C++ at once. However, I want to implement the methods for creating and modifying the mesh in Python, because flexibility is more important than speed. After reading a lot, there seem to be three main approaches to doing this. I need help choosing between: 1. Create the data portions of the mesh class in C++ and use Boost to expose it to Python as a module. Then use Python to add methods, as shown in the Tutorial, and pass the whole object back to C++. Finally, use <extract> to get C++ values for computation. One downside to this approach is that apparently Python can't be used to implement a constructor method for a wrapped C++ class. 2. Similar to #1, but instead create Python classes that inherit from the C++ base classes, and then add Python methods. Not sure how to get the resulting objects back into C++. 3. Create the data and methods in Python, and then define custom lvalue converters to get the data into C++. This seems messy because I have to use the classic Python/C API in the converter functions, which seems to kind of defeat the purpose of using Boost. Your input is greatly appreciated! If I have misunderstood any thing, please let me know. The resulting code will be made available as an example to others. Craig Finch -------------- Please reply to cfinch(a)ieee.org __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

2 5