Mailman 3 May 2008 - Cplusplus-sig

Re: [C++-sig] Smart Pointers in Boost.Python with Automatic Dereferencing
by Ralf W. Grosse-Kunstleve May 20, 2008

May 20, 2008

Boost.Python has special support for boost::shared_ptr<>. E.g. this should do what you want (untested): class_<A, shared_ptr<A> >("A") It is more difficult only if you have your own smart pointers. Ralf ----- Original Message ---- From: "Bilokon, Paul" <paul.bilokon(a)lehman.com> To: Development of Python/C++ integration <c++-sig(a)python.org> Sent: Monday, May 19, 2008 5:30:59 AM Subject: [C++-sig] Smart Pointers in Boost.Python with Automatic Dereferencing Hi all, I'm trying to find an authoritative resource on exposing functions that return smart pointers using Boost.Python. So far my best example is this: http://wiki.python.org/moin/boost.python/PointersAndSmartPointers However, I find the need to explicitly dereference the pointer in Python deeply unsatisfactory: print (+an_A).hello() This is essentially C++ programming in Python. The whole purpose of the exercise is to avoid the need for explicit memory management! Is there another method that will simply allow me to call print an_A.hello() Many thanks for your help! Best wishes, Paul P.S. Just for your information I'll paste the C++ code: #include <boost/shared_ptr.h> using namespace boost; struct A { shared_ptr<A> create () { return shared_ptr<A>(new A); } std::string hello () { return "Just nod if you can hear me!"; } }; BOOST_PYTHON_MODULE(shared_ptr) { class_<A>("A",init<>()) .def("create",&A::create,return_value_policy<return_by_value>()) .staticmethod("create") .def("hello",&A::hello) ; class_< shared_ptr<A> >("A_ptr", init<const shared_ptr<A>& >()) .def("__pos__",&boost::shared_ptr<A>::get,return_internal_reference<>()) ; } And the sample Python program: from shared_ptr import * an_A = A_ptr.create() print (+an_A).hello() - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - This message is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers. Email transmission cannot be guaranteed to be secure or error-free. Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such. All information is subject to change without notice. _______________________________________________ C++-sig mailing list C++-sig(a)python.org http://mail.python.org/mailman/listinfo/c++-sig

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Re: [C++-sig] Non-const reference arguments and from_python conversions
by Ralf W. Grosse-Kunstleve May 20, 2008

May 20, 2008

> Does this mean the argument MUST be passed by const-reference or by > value (i.e. it can't be a non-const reference or a pointer)? Yes. -- A few years ago we had a contract with David to implement support for "converters with write-back", but it turned out to be too difficult. In theory you can use indirection of some sort to get around the problem (e.g. make a proxy object holding a reference to the object you actually want to pass, pass the proxy by value). However, in most cases this will probably impose unacceptable restrictions on the interface. Ralf

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Non-const reference arguments and from_python conversions
by Bilokon, Paul May 20, 2008

May 20, 2008

Hi all, I have written a from_python_stream converter for Python streams (like sys.stdout). The converter registers itself as follows: boost::python::converter::registry::push_back( &convertible, &construct, boost::python::type_id<_Stream>()); So nothing unusual here. _Stream is the template argument. Then I do the following: StreamConversions::from_python_stream<reference_wrapper<ostream> >(); Again, nothing unusual here. I'm testing it on two functions: void outTest(const ostream & out) { // cout << "Test-----outTest successful" << endl; } void outTestRef(ostream & out) { cout << "Test-----outTest successful" << endl; } Which are registered like this: def("outTest", outTest); def("outTestRef", outTestRef); Obviously I need outTestRef to work. Otherwise I can't use operator<<, so what's the point. Unfortunately, outTest works, outTestRef does not work: outTest(sys.stderr) # works outTestRef(sys.stderr) # fails The error is: File "proto_test.py", line 23, in <module> outTestRef(sys.stderr) Boost.Python.ArgumentError: Python argument types in pyamp.proto.outTestRef(file) did not match C++ signature: outTestRef(class std::basic_ostream<char,struct std::char_traits<char> > {lvalue}) Hence the question: is there absolutely no support for non-const reference arguments? Many thanks for your help! Regards, Paul - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - This message is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers. Email transmission cannot be guaranteed to be secure or error-free. Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such. All information is subject to change without notice.

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Re: [C++-sig] Smart Pointers in Boost.Python with AutomaticDereferencing
by Ralf W. Grosse-Kunstleve May 20, 2008

May 20, 2008

No, sorry. Very wild idea: can your smart pointer be converted both ways to/from a boost::shared_ptr? And are all your smart pointer objects passed by value or const&? Then maybe a custom rvalue converter could do the trick. I hope someone else with actual experience in this area will be able to help. Ralf ----- Original Message ---- From: "Bilokon, Paul" <paul.bilokon(a)lehman.com> To: Development of Python/C++ integration <c++-sig(a)python.org> Sent: Monday, May 19, 2008 10:18:38 AM Subject: Re: [C++-sig] Smart Pointers in Boost.Python with AutomaticDereferencing Hi Ralf, Many thanks for your reply. Unfortunately, I do have a custom "smart" pointer and it would be very difficult to convert it. Do you know if there are any code examples for custom smart pointers? Many thanks, Paul -----Original Message----- From: c++-sig-bounces(a)python.org [mailto:c++-sig-bounces@python.org] On Behalf Of Ralf W. Grosse-Kunstleve Sent: Monday, May 19, 2008 5:52 PM To: Development of Python/C++ integration Subject: Re: [C++-sig] Smart Pointers in Boost.Python with AutomaticDereferencing Boost.Python has special support for boost::shared_ptr<>. E.g. this should do what you want (untested): class_<A, shared_ptr<A> >("A") It is more difficult only if you have your own smart pointers. Ralf ----- Original Message ---- From: "Bilokon, Paul" <paul.bilokon(a)lehman.com> To: Development of Python/C++ integration <c++-sig(a)python.org> Sent: Monday, May 19, 2008 5:30:59 AM Subject: [C++-sig] Smart Pointers in Boost.Python with Automatic Dereferencing Hi all, I'm trying to find an authoritative resource on exposing functions that return smart pointers using Boost.Python. So far my best example is this: http://wiki.python.org/moin/boost.python/PointersAndSmartPointers However, I find the need to explicitly dereference the pointer in Python deeply unsatisfactory: print (+an_A).hello() This is essentially C++ programming in Python. The whole purpose of the exercise is to avoid the need for explicit memory management! Is there another method that will simply allow me to call print an_A.hello() Many thanks for your help! Best wishes, Paul P.S. Just for your information I'll paste the C++ code: #include <boost/shared_ptr.h> using namespace boost; struct A { shared_ptr<A> create () { return shared_ptr<A>(new A); } std::string hello () { return "Just nod if you can hear me!"; } }; BOOST_PYTHON_MODULE(shared_ptr) { class_<A>("A",init<>()) .def("create",&A::create,return_value_policy<return_by_value>()) .staticmethod("create") .def("hello",&A::hello) ; class_< shared_ptr<A> >("A_ptr", init<const shared_ptr<A>& >()) .def("__pos__",&boost::shared_ptr<A>::get,return_internal_reference<>()) ; } And the sample Python program: from shared_ptr import * an_A = A_ptr.create() print (+an_A).hello() - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - This message is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers. Email transmission cannot be guaranteed to be secure or error-free. Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such. All information is subject to change without notice. _______________________________________________ C++-sig mailing list C++-sig(a)python.org http://mail.python.org/mailman/listinfo/c++-sig _______________________________________________ C++-sig mailing list C++-sig(a)python.org http://mail.python.org/mailman/listinfo/c++-sig - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - This message is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers. Email transmission cannot be guaranteed to be secure or error-free. Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such. All information is subject to change without notice. _______________________________________________ C++-sig mailing list C++-sig(a)python.org http://mail.python.org/mailman/listinfo/c++-sig

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build error??
by Michael Wieher May 19, 2008

May 19, 2008

It looks like build_ext / distutils is failing to understand some parameters correctly? [michael@majw src]$ python setup-mempy.py build_ext -i running build_ext building 'pymem' extension gcc -pthread -fno-strict-aliasing -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -D_GNU_SOURCE -fPIC -fPIC -I/usr/include/python2.4 -c libraries/classlib/dataset.cpplibraries/classlib/synobj.cpp -o build/temp.linux-i686-2.4/libraries/classlib/dataset.cpplibraries/classlib/synobj.o gcc: libraries/classlib/dataset.cpplibraries/classlib/synobj.cpp: No such file or directory gcc: no input files error: command 'gcc' failed with exit status 1 ----------------------------------------------------------------------------------------------------------------------------- #!/usr/bin/python from distutils.core import setup,Extension module1 = Extension('pymem', include_dirs=[ # '/home/michael/proj/pydata/src' # '/home/michael/proj/pydata/src/libraries', # '/home/michael/proj/pydata/src/libraries/support', # '/home/michael/proj/pydata/src/libraries/classlib', ], sources=[ 'memrid.cpp', 'libraries/datainit.cpp', 'libraries/classlib/dataset.cpp' 'libraries/classlib/synobj.cpp' # 'libraries/classlib/stack.cpp' # 'libraries/classlib/datarequest.cpp' # 'libraries/classlib/initdata.cpp' # 'libraries/classlib/bitvectorlib.cpp' ], ) setup(name='pymem', version='1.0', description='pythonextensioninC', ext_modules=[module1]) ----------------------------------------------------------------------------------------------------------------------------- Seems pretty simple! but as I uncomment further dependent libraries, it just starts getting confused and dies... any idea? looks like it forgets spaces somehow.. I'm not sure whats going on...

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?? building the shared library issue
by Michael Wieher May 19, 2008

May 19, 2008

Problem: ------------- using python <setup-script>py build_ext -i my <setup-script> is not correct. The source="file.cpp" fle has an include and the included include includes other "name.h" files the object files are not being linked to the final library correctly how do I tell distutils how to handle multiple source-files when building my extensions?

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Smart Pointers in Boost.Python with Automatic Dereferencing
by Bilokon, Paul May 19, 2008

May 19, 2008

Hi all, I'm trying to find an authoritative resource on exposing functions that return smart pointers using Boost.Python. So far my best example is this: http://wiki.python.org/moin/boost.python/PointersAndSmartPointers However, I find the need to explicitly dereference the pointer in Python deeply unsatisfactory: print (+an_A).hello() This is essentially C++ programming in Python. The whole purpose of the exercise is to avoid the need for explicit memory management! Is there another method that will simply allow me to call print an_A.hello() Many thanks for your help! Best wishes, Paul P.S. Just for your information I'll paste the C++ code: #include <boost/shared_ptr.h> using namespace boost; struct A { shared_ptr<A> create () { return shared_ptr<A>(new A); } std::string hello () { return "Just nod if you can hear me!"; } }; BOOST_PYTHON_MODULE(shared_ptr) { class_<A>("A",init<>()) .def("create",&A::create,return_value_policy<return_by_value>()) .staticmethod("create") .def("hello",&A::hello) ; class_< shared_ptr<A> >("A_ptr", init<const shared_ptr<A>& >()) .def("__pos__",&boost::shared_ptr<A>::get,return_internal_reference<>()) ; } And the sample Python program: from shared_ptr import * an_A = A_ptr.create() print (+an_A).hello() - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - This message is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers. Email transmission cannot be guaranteed to be secure or error-free. Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such. All information is subject to change without notice.

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Re: [C++-sig] Merging indexing_v2 to mainline
by Ralf W. Grosse-Kunstleve May 18, 2008

May 18, 2008

Hi Raoul, Nice to hear from you! Is indexing_v2 fully backward compatible with the current indexing suite? If not, is it technically feasible to change indexing_v2 so that it can co-exist with the current indexing suite? After so many years, I fear too many things will break if indexing_v2 isn't fully backward compatible. But it would be very nice if it were generally available. Ralf

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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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python::object that takes ownership of a C++ instance
by Francis Moreau May 17, 2008

May 17, 2008

Hi, I would like to know if there is the equivalent of manage_new_object return_policy but for an argument pass to Python? I have a Python class derived from a C++ base class: class PyEventProcessor(CppEventProcessor): def processEvent(in_event): # do something And then in C++ I want to call processEvent and transferring the ownership of the event to Python: void CppEventProcessor_Wrapped::pyProcessEvent(const Event& in_event) { // This following line is working well, but I want to transfert the ownership of the event instead of passing a reference on it. return python::call_method<void>(m_pSelf, "processEvent", boost::ref(in_event)): // I tried something like this but it's not working. Event* pNewEvent = in_event.clone(); python::object obj(&pNewEvent); // Event is a type exposed in Python } I would like to know what is the best way to do something like this, is it by using a auto_ptr, or a from_python convertor, or something else? Also, I have a few types richer than Event, and exposed to Python too, and I want to be able to use them directly in Python, e.g.: class PyEventProcessor(CppEventProcessor): def processEvent(in_event): if in_event is ConnectionEvent: srcAddr = in_event.getSourceAddr() Thanks, Francis

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