Mailman 3 July 2006 - Cplusplus-sig

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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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 ?

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Exposing c++ classes with static arrays using Boost.Python and py++
by Abhi Oct. 3, 2006

Oct. 3, 2006

While running py++ on a class with a static array inside it, py++ generates Boost.Python bindings using a derived class for the original C++ class. Let me illustrate with the help of the following example: class AttributesTest { public: int staticIntArray[10]; }; Notice this class has an array inside it Running py++ generates the following code, with a wrapper class that derives from the AttributesTest class. struct AttributesTest_wrapper : AttributesTest, bp::wrapper< AttributesTest > { AttributesTest_wrapper(AttributesTest const & arg ) : AttributesTest( arg ) , bp::wrapper< AttributesTest >() {} AttributesTest_wrapper( ) : AttributesTest( ) , bp::wrapper< AttributesTest >() {} pyplusplus::containers::static_sized::array_1_t< int, 10 > pyplusplus_staticIntArray_wrapper(){ return pyplusplus::containers::static_sized::array_1_t< int, 10 >( staticIntArray ); } }; and BOOST_PYTHON_MODULE(PYPP_YodaPacketCommon){ if( true ){ typedef bp::class_< AttributesTest_wrapper > AttributesTest_exposer_t; AttributesTest_exposer_t AttributesTest_exposer = AttributesTest_exposer_t( "AttributesTest" ); bp::scope AttributesTest_scope( AttributesTest_exposer ); AttributesTest_exposer.def( bp::init< >()[bp::default_call_policies()] ); pyplusplus::containers::static_sized::register_array_1< int, 10, bp::default_call_policies >( "__array_1_int_10" ); AttributesTest_exposer.add_property( "staticIntArray" , bp::make_function( (pyplusplus::containers::static_sized::array_1_t< int, 10 > ( AttributesTest_wrapper::* )( ) )(&AttributesTest_wrapper::pyplusplus_staticIntArray_wrapper) , bp::with_custodian_and_ward_postcall< 0, 1, bp::default_call_policies >() ) );; Note that it maps the python name "AttributesTest" to the derived class AttributesTest_wrapper. Why not just keep it simple and rather than creating a derived class just map the variable "staticIntArray" via a global method, such as: .add_property( "staticIntArray" , bp::make_function( (&::someglobal_staticIntArray_wrapper) , bp::with_custodian_and_ward_postcall< 0, 1, bp::default_call_policies >() ) );; and define the someglobal_staticIntArray_wrapper method as: pyplusplus::containers::static_sized::array_1_t< int, 10 > someglobal_staticIntArray_wrapper(){ return pyplusplus::containers::static_sized::array_1_t< int, 10 >( staticIntArray ); } Is there any drawback with just mapping the array variable to a global method rather than mapping the whole class. thanks - Abhi

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boost:python::arg and default value
by Roman Yakovenko Sept. 1, 2006

Sept. 1, 2006

Hi. I want to resolve the issue discussed in this thread: http://thread.gmane.org/gmane.comp.python.c++/9878/focus=9881 The short version of the discussion is: class Foo; class Foo2 { friend class Foo; Foo2(Foo *f=0); }; class Foo { Foo(Foo2 *f=0); }; It is not possible to expose both Foo and Foo2 constructors with default values, without usage of some tricks. The main problem is that, when Boost.Python initializes boost::python::arg, it requires type of default value to be registered. I had some free time and took a look on the code. I think, I understand what is going on and how to fix the situation, but still need some help here and there. I see only one possible solution - to add to Boost.Python functionality, that will allow user to control argument default value conversion time. Today, the default value converted to Python during function registration. This happens in boost::python::objects::function class constructor. Solution: 1. To add classes that will define C++ to Python convert time. struct converter_base{ virtual handle<> py_value() const = 0; //const in interface is a hack, objects::function::call member function //has const modifier }; struct default_converter : converter_base{ converts value in the constructor and saves the value in a member variable py_value returns the member variable }; struct on_first_use_converter : converter_base{ saves the C++ value as member variable py_value will convert C++ value to Python on first invocation, will save the result in member variable, after this, it will always return the member variable. }; 2. Change in keyword struct. Today keyword struct keeps function default value as instance of handle<>. This should be changed. keyword struct should keep shared_ptr to coverter_base class instance or it should keep empty shared_ptr. Thus it will be possible to control C++ to Python default value conversion time from objects::function class. 3. There are few changes, that should be done to boost::python::objects::function class. This is the place I have lack of knowledge and the code is a little bit complex and fragile. More over, every additional logic, that will be added here will downgrade performance. There are few changed that should be done to the class. 1. The class should keep all keywords, that has default value converter other than default_converter. It also should save keyword position. 2. In constructor, when we register function keyword arguments, we should skip initialization of default value, for converters other than default_converter. 3. Now, the only change left is to modify function::call method. Unfortunately I can not write the working code - lack of knowledge( or sleep ). I'll be glad, if somebody can help me here. The main problem, is that some how I should pass to the function default values and I don't exactly understand how I should do that. I attached the modified files. What do you think about those changes? -- Roman Yakovenko C++ Python language binding http://www.language-binding.net/

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boost python liking problems
by Eduardo Picado Aug. 9, 2006

Aug. 9, 2006

Hi, I'm trying to use Boost Python to wrap a 3rd party library. I have the headers, DLLs and a .lib file. When I try to compile my .cpp files I receive linkage errors: ------------- Creating library bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.lib and object bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.exp TASRNlSmlResult.obj : error LNK2001: unresolved external symbol "public: char const * __thiscall TASRNlSmlResult::str(void)const " (?str@TASRNlSmlResult@@QBEPBDXZ) …....... "link" /nologo /INCREMENTAL:NO /DEBUG /DLL /subsystem:console /out:"bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.pyd" /IMPLIB:"bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.lib " /LIBPATH:"c:\python22\libs" /LIBPATH:"bin\boost\libs\python\build\boost_python.dll\msvc\debug\threading-multi" /LIBPATH:"C:\PROGRA~1\MICROS~4\VC98\lib" "boost_python.lib" @"bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.CMD" ...failed vc-Link bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.pyd bin\telismaPyste\TASRNlSmlResult.pyd\msvc\debug\threading-multi\TASRNlSmlResult.lib... ...failed updating 1 target... --------------- I'm using bjam with canonical options. I guess I'm not correcting specifying where is the .lib file. How can I do this? Any ideas? Thanks, Eduardo Picado

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Working with python unicode strings without wstring
by Rod Cloutier Aug. 6, 2006

Aug. 6, 2006

Hi, I am trying to wrap an external library that uses "const wchar_t *" a arguments for several methods. I know that if they would have used std::wstring the conversion would have been straight forward. Is there anyway to convert python unicode string to wchar_t pointers ? Can I make the following code work without writting a wrapper function that uses a wstring as an argument ? in C++: void printText( const wchar_t* str ) { std::wcout << str; } in python: MyModule.printText( u"The message" ) Thanks Rodrigue Cloutier

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Pyplusplus - anonymous union
by Jan Langer Aug. 2, 2006

Aug. 2, 2006

Hello, I'm using pyplusplus to generate python-bindings for a C API. However, there are several unions, and I just don't know how to handle them. The following example code from the API: typedef struct { int offset; int dataType; union { char *sdata; int idata; } u; } A; generates this Boost.Python code: bp::class_< A >( "A" ) .def_readwrite( "offset", &A::offset ) .def_readwrite( "dataType", &A::dataType ) .def_readonly( "u", &A::u ); and it does not compile on gcc 3.3.2 with this error: error: template-argument `A::<anonymous union> A::*' uses anonymous type Is there a solution? I have already searched the news archives, but haven't found useful hints. Thanks, Jan

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implicit conversion from python list
by James Pelletier July 31, 2006

July 31, 2006

I'm trying to create an implicit conversion from a native python list to a user-defined C++ object. The conversion seems to work fine for an integer, but the same conversion doesn't seem to work for a list. Is this supported (I'm using boost-1.32)? James ------------- test.C -------------- #include <boost/python.hpp> using namespace boost::python; class X { public: X(int) {} X(list) {} }; void f( X ) {} BOOST_PYTHON_MODULE(boostpy) { class_<X>( "X", init<int>()[return_value_policy<manage_new_object>()] ) .def( init<list>()[return_value_policy<manage_new_object>()] ); implicitly_convertible<int, X>(); implicitly_convertible<list, X>(); def( "f", &f ); } ----------------------------------- >>> from boostpy import * >>> X(32) <boostpy.X object at 0x81daeb4> >>> X([]) <boostpy.X object at 0x81dd374> >>> f(32) >>> f(X([])) >>> f([]) Traceback (most recent call last): File "<stdin>", line 1, in ? Boost.Python.ArgumentError: Python argument types in boostpy.f(list) did not match C++ signature: f(X) >>>

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Converting a python dictionary rvalue to a T* in boost.python
by Kevin Jones July 31, 2006

July 31, 2006

Hi all, I have a c++ class T that implements an extended table. Additionally, I have a C++ function that takes a T* as an argument void (E.g. - f(T* t) ). How do I create converter to convert an arbitrary python dictionary in boost.python to a T* as an argument? The doucmentation is sparse and I have not found any comparable examples. Thanks in advance __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Boost.Python to use non-standard python location on OS X
by Roberto Aguilar July 29, 2006

July 29, 2006

Hello, I'm trying to build the example Boost.Python project on OS X using the python version 2.4.2 provided by Fink, which is installed at: /sw/bin/python The includes and libraries are: /sw/include/python2.4 /sw/lib/python2.4 I set the following in my Jamrules file: PYTHON_VERSION = 2.4 ; PYTHON_ROOT = /sw ; PYTHON_INCLUDES = /sw/include/python2.4 ; PYTHON_LIB_PATH = /sw/lib/python2.4 ; But, when I build, it seems that the resulting module is still linking to /usr/bin/python, which is version 2.3. Trying to use the module using /sw/bin/python results in: ---- [berto@drjekyll][713]$ /sw/bin/python Python 2.4.2 (#1, Mar 22 2006, 18:15:19) [GCC 4.0.1 (Apple Computer, Inc. build 5250)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import data Fatal Python error: Interpreter not initialized (version mismatch?) Abort trap ---- But using /usr/bin/python, everything works well. I then thought the problem was that I built boost without specifying the non-standard location so I recompiled using: ---- bjam -sTOOLS=darwin -sPYTHON_ROOT=/sw -sPYTHON_VERSION=2.4 -sPYTHON_INCLUDES=/sw/include/python2.4 -sPYTHON_LIB_PATH=/sw/lib/python2.4 -a ---- Still no luck. Any ideas are greatly appreciated. Thanks! -Roberto.

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