Mailman 3 October 2010 - Cplusplus-sig

Inheritance problem
by Erik Türke Oct. 24, 2010

Oct. 24, 2010

Hi! I am trying to expose some c++ classes with boost.python. Unfortunately, i have some trouble with the inheritance of classes which need a wrapper. It is something like that: class Base { public: void someFunction() { doSomething; } }; class BaseWrapper : public Base, boost::python::wrapper<Base> { public: //constructor here void someFunctionWrapped() { doSomeThing and call Base::someFunction(); } private: PyObject *self; }; class Derived : public Base {}; class DerivedWrapper : public Derived, boost::python::wrapper<Derived> { public: //constructor here private: PyObject *self; }; BOOST_PYTHON_MODULE( myModule ) { class_<Base, BaseWrapper ("Base", init<>() ) .def( "someFunction", &BaseWrapper::someFunctionWrapped); class_<Derived, DerivedWrapper, bases<Base> > ("Derived", init<>()); } In Python: import myModule derived = myModule.Derived() derived.someFunction() This crashes with a signature error: Boost.Python.ArgumentError: Python argument types in Base.someFunction(Derived) did not match C++ signature: someFunction(isis::python::BaseWrapped {lvalue}) If the function (here someFunction(Wrapped) ) was not declared in the wrapper class, it works. But unfortunately i need it there. Is someone aware of this problem and can give me a hint? Thanks for your help! Best regards! Erik Türke Department of Neurophysics Max-Planck-Institute for Human Cognitive and Brain Sciences Stephanstrasse 1A 04103 Leipzig Germany Tel: +49 341 99 40-2440 Email: tuerke(a)cbs.mpg.de www.cbs.mpg.de

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Creating non-naive datetime objects in C++
by Grant Mckenzie Oct. 22, 2010

Oct. 22, 2010

Hi, I am writing some C++ code and importing into python via swig. I'd like to pass datetime objects to pass back to python. The following code will create a naive datetime after including datetime.h. PyObject* ret = PyDateTimeAPI->DateTime_FromDateAndTime( y, m, d, h, m, s, u, Py_None, PyDateTimeAPI->DateTimeType); I'd like to create a datetime object with UTC timezone info set. Much to my chagrin, I am having lots of trouble finding an example of how to do this. Any help would be appreciated. Regards, Grant.

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boost::python + python3.1.2 throw
by Neal Becker Oct. 20, 2010

Oct. 20, 2010

Has behavior of c++ exception changed with boost::python + python3? I used to simply use throw from c++. Now I get: SystemError: initialization of ldpc_45 raised unreported exception I believe this exception was really: if (!fp) throw std::runtime_error ((boost::format ("fopen %1% failed") % name).str()); which would have produced a good error message under python2.6.

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Using C++ classes exposed by other modules
by Bryant Gipson Oct. 19, 2010

Oct. 19, 2010

Hi All, Maybe a simple question, maybe not: I have a binary-only module which was automatically generated by Py++ and its associated pre-compiled C++ libraries. There's a basic C++ type "A" which was exposed along with plenty of support functions in the associated C++ library which operate on it in both C++ and Python. i.e. python: a = mod.A(); mod.helpfulFunction(a); >>Some helpful output. My problem is now I want to write a module which operates on the C++ class A. C++: void mySlightlyHelpfulFunction(cppmodule::A &a) { ... } BOOST_PYTHON_MODULE(myModule) { def("mySlightlyHelpfulFunction",mySlightlyHelpfulFunction); } Python: a = mod.A() myModule.mySlightlyHelpfulFunction(a) myModule.mySlightlyHelpfulFunction(A) did not match C++ signature: mySlightlyHelpfulFunction(mod::A {lvalue}) I've also tried this with Py++ with the same results. Thus far it appears that no converter has been globally registered by the module mod. Any help would be hugely appreciated. I apologise if this is a trivial question, I'm still new to hybrid C++/python. Thanks.

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building boost python --threading mystery ?
by Avi Bahra Oct. 15, 2010

Oct. 15, 2010

Trying to understand --threading option when applied to building boost python On Linux with gcc it appears to have no effect. bjam toolset=gcc --with-python link=shared variant=debug --threading=single Building the Boost C++ Libraries. ...patience... ...patience... ...found 1489 targets... ...updating 40 targets... common.mkdir bin.v2 common.mkdir bin.v2/libs common.mkdir bin.v2/libs/python common.mkdir bin.v2/libs/python/build common.mkdir bin.v2/libs/python/build/gcc-4.2.1 common.mkdir bin.v2/libs/python/build/gcc-4.2.1/debug common.mkdir bin.v2/libs/python/build/gcc-4.2.1/debug/threading-multi gcc.compile.c++ bin.v2/libs/python/build/gcc-4.2.1/debug/threading-multi/numeric.o When I specify "--threading=single" it appears to be ignored: Even putting a rubbish value has no effect ? --threading=gooblygook bjam toolset=gcc --with-python link=shared variant=debug --threading=gooblygook nBuilding the Boost C++ Libraries.nn ...patience... ...patience... ...found 1489 targets... ...updating 19 targets... gcc.compile.c++ bin.v2/libs/python/build/gcc-4.2.1/debug/threading-multi/object/function.o However if you have Jamfile that has "using python" like boost python examples then it gets built as : bjam ...patience... ...patience... ...patience... ...found 12311 targets... ...updating 42 targets... common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2 common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1 common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1/debug gcc.compile.c++ /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1/debug/numeric.o gcc.compile.c++ /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1/debug/list.o This time there is no mention of threading ? So it appears that when building boost python at $BOOST_ROOT level it is fixed as multi threaded but then gets ignored when building python extensions. The net result being two builds of boost python. Best regards, Avi

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Docstrings question
by Michael Wild Oct. 15, 2010

Oct. 15, 2010

Hi all I'm fairly new to Boost.Python and currently I'm looking for a convenient way of adding docstrings to overloaded operators, e.g: class A; class B A operator+(A const&, A const&); B operator+(B const&, B const&); BOOST_PYTHON_MODULE(foo) { bp::class_<A>("A") .def(self + self) //< How to add docstring here? } I know I could also use: A (*A_add_op)(A const&, A const&) = operator+; bp::class_<A>("A") .def("__add__", A_add_op, "Add two A objects") or a direct cast, but honestly, I don't look forward to all that typing, and it is so much harder to read than the first option. Thanks for the help Michael

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Fwd: Re: shared_ptr and register_ptr_to_python
by Marek Denis Oct. 10, 2010

Oct. 10, 2010

On 10.10.2010 03:47, Jim Bosch wrote: > > Pretty much everything you need should automatically work, whether you > use shared_ptr or raw pointers with call policies. If you've invoked > register_ptr_to_python on all the classes you're using, That's what I couldn't get while reading Boost tutorial (the example code didn't work either :( ). Let's say I have three classes: class A {}; class B : public A {}; class C : public B {}; should I later just put: register_ptr_to_python< A >(); register_ptr_to_python< B >(); register_ptr_to_python< C >(); ? > you'll find that > in Python you'll always get the most-derived class, even if it's > returned as a base class pointer or smart pointer on the C++ side. Here is the small code snippet: +v boost::python::call_method<void>(callback,"addToQueue",c); -v where callback is a PyObject* pointer,and 'c' is a pointer to the object. Whenever I call this instruction, I can see that the 'c' object is being copied (I just put some cout << "debug" << endl in the definition of the Copy Constructor), so I assumed that Python code doesn't operate on the object that was created in C++ module. Instead, it just operates on the copy. > You shouldn't need any extra compiler flags. Just use Boost.Python the > way described in the tutorial, and throw in some register_ptr_to_python > invocations - that should be all you need. -- best wishes Marek Denis

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shared_ptr and register_ptr_to_python
by Marek Denis Oct. 10, 2010

Oct. 10, 2010

Hello list, What I am trying to achieve is a part of C++ code operating on some data nad 'putting' some C++ defined (as well as Python exposed) objects into the Python blocking queues. Is there any possibility for Python to work directly on the C++ objects? Right now, when I launch the Python function from withing the C++ code, passing the POINTER (just normal pointer) od my objects what I can observer is a process of creating and copying the new object in Python. I can then operate on this object and so on, however I truly believe that working on the same object would be faster. Another problem is that I need to use some polymorphism functionality, so I would like to be able to put a object of type Derived from withing C++ code, get it from the Python perspective as Base object and launch virtual function (which would be Derived::f in this case). I am still not sure whether passing shared_ptr and using register_ptr_to_python is what I really need, wherether there is ANY possibility to do what I actually need. In other words I am creating objects with C++ but want to operate on them with Python, preferably with all the polimorphism and that fancy stuff. Any code snippets, suggestions? BTW. What options shall I pass to g++ in order to use shared_ptr? Thank you in advance, -- best regards Marek Denis [marek(a)octogan.net]

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Fw: [cfe-dev] Is Boost-Python tested?
by Bryce Lelbach Oct. 7, 2010

Oct. 7, 2010

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello list, I'm a Boost regular - happened to come across this on the clang developer's list. I responded briefly to it, but I don't really have any knowledge of Boost.Python's internals. Therefore, forwarding it to you guys :P. - - Bryce Lelbach Begin forwarded message: Date: Wed, 06 Oct 2010 19:32:40 +0200 From: Riccardo Rossi <rrossi(a)cimne.upc.edu> To: cfe-dev(a)cs.uiuc.edu Subject: [cfe-dev] Is Boost-Python tested? Dear list, during the last two days i have been compiling my research code (around 500k lines of c++) using clang (clang 2.9 as downloaded from the svn 2 days ago). My code relies hevily on boost python.In doing my compilation i first compiled boost1.44 with clang (which went fine) and i later used it in compiling my code. Apart for minor issues the compilation went fine and the code runs correctly through the benchamrk example, HOWEVER on exit i get a segmentation fault. The segmentation fault is also confirmed by valgrind. Our code has been tested (and works correctly) using gcc, intel, sun and msvc (this last one in windows), and provides a pretty clean valgrind output (at least as clean as the boost python hello world example). I am honestly a bit surprised of having such a segfault on our test examples, and i was wandering if the boost_python stuff has been tested, in particular with reference to the allocation of "internal_references". please find attached the output of valgrind for the case of interest, where i just load our library in python and i close the program. for reference the gcc output (intel's is very similar) finishes with HEAP SUMMARY: ==6879== in use at exit: 1,866,386 bytes in 3,436 blocks ==6879== total heap usage: 9,373 allocs, 5,937 frees, 4,125,837 bytes allocated ==6879== ==6879== LEAK SUMMARY: ==6879== definitely lost: 0 bytes in 0 blocks ==6879== indirectly lost: 0 bytes in 0 blocks ==6879== possibly lost: 368,951 bytes in 361 blocks ==6879== still reachable: 1,497,435 bytes in 3,075 blocks ==6879== suppressed: 0 bytes in 0 blocks As a secondary thing, i wanted to comment that the compilation time is not better than gcc. I compiled the clang myself, so i probably did somethign wrong. In particular i attempted habilitating optimization, but i probably skipped something to have optimal performance. Any suggestion on how to make it faster? thank you in advance for any suggestion you can provide Riccardo - -- ________________________________________________________________ Riccardo Rossi, Ph.D, Civil Engineer member of the Kratos Group: kratos.cimne.upc.es Centro Internacional de Métodos Numéricos en Ingeniería (CIMNE) Universidad Politécnica de Cataluña (UPC) Edificio C-1, campus Norte UPC Gran Capitan, s/n 08034 Barcelona, España Tel. (+34) 93 401 73 99 ________________________________________________________________ AVISO IMPORTANTE Los datos de carácter personal contenidos en el mensaje, se registrarán en un fichero para facilitar la gestión de las comunicaciones de CIMNE. Se pueden ejercitar los derechos de acceso, rectificación, cancelación y oposición por escrito, dirigiéndose a nuestras oficinas de CIMNE, Gran Capitán s/n, Edificio C1 - Campus Norte UPC, 08034 Barcelona, España. AVÍS IMPORTANT Les dades de caràcter personal contingudes en aquest missatge es registraran en un fitxer per facilitar la gestió de les comunicacions del CIMNE. Es poden exercir els drets d'accés, rectificació, cancel·lació i oposició, per escrit a les nostres oficines del CIMNE, Gran Capità s/n, Edifici C1, Campus Nord UPC, 08034 Barcelona, Espanya. IMPORTANT NOTICE All personal data contained in this mail will be processed confidentially and stored in a file property of CIMNE in order to manage corporate communications. You may exercise the right of access, rectification, deletion and objection by letter sent to CIMNE, Gran Capitán, Edificio C1 - Campus Norte UPC, 08034 Barcelona, Spain. - -- Bryce Lelbach aka wash http://groups.google.com/group/ariel_devel -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkytYOMACgkQO/fqqIuE2t6XMACfQRIia28fmKvxWTAqkvz+dWJ0 HwAAoNrwy2DaOCVsb40u7K0lm9UPSIEe =512P -----END PGP SIGNATURE----- _______________________________________________ cfe-dev mailing list cfe-dev(a)cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev

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Using boost.python with Makefile (no bjam)
by Philipp Münzel Oct. 6, 2010

Oct. 6, 2010

Oh crap, the command that links is of course: $ g++ -shared -Wl,-soname,"libhello.so" -L/usr/local/lib -lboost_python -o libhello.so hello.o But I get the undefined symbols nevertheless: U PyString_Type w _Jv_RegisterClasses U _Py_NoneStruct U _Unwind_Resume@@GCC_3.0 U _ZN5boost6python6detail11init_moduleEPKcPFvvE U _ZN5boost6python6detail12gcc_demangleEPKc U _ZN5boost6python6detail17scope_setattr_docEPKcRKNS0_3api6objectES3_ U _ZN5boost6python7objects15function_objectERKNS1_11py_functionE U _ZN5boost6python7objects21py_function_impl_baseD2Ev U _ZN5boost6python9converter19do_return_to_pythonEPKc U _ZN5boost6python9converter8registry5queryENS0_9type_infoE U _ZNK5boost6python7objects21py_function_impl_base9max_arityEv U _ZNK5boost6python9converter12registration25expected_from_python_typeEv U _ZTIN5boost6python7objects21py_function_impl_baseE U _ZTIPKc@@CXXABI_1.3 U _ZTIc@@CXXABI_1.3 U _ZTVN10__cxxabiv120__si_class_type_infoE@@CXXABI_1.3 U _ZTVN5boost6python7objects21py_function_impl_baseE U _ZdlPv@@GLIBCXX_3.4 U _Znwj@@GLIBCXX_3.4 U __cxa_atexit@@GLIBC_2.1.3 w __cxa_finalize@@GLIBC_2.1.3 U __cxa_guard_abort@@CXXABI_1.3 U __cxa_guard_acquire@@CXXABI_1.3 U __cxa_guard_release@@CXXABI_1.3 w __gmon_start__ U __gxx_personality_v0@@CXXABI_1.3

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