Mailman 3 March 2005 - Cplusplus-sig

boost/python: how to: call memberfunctions of an existing c++ object from python?
by Marco Borm March 10, 2005

March 10, 2005

(I also posted this message to gmane.comp.lib.boost.devel) Hi Boost/Python developers, at first I have to say that I am no boost nor a python expert. I've searched for hours now on the web for my problem but was unable to find some solution for my problem: Currently I am working on the possibility that an python-script is called by an existing c++ object. This was "easy" to do with and without the boost python-classes. To make this more complicate, the script must be able to call some member functions of this object. So to make this possible I created an BOOST_PYTHON_MODULE() containing the class and the to be called member function-definitions. Now it is possible to create new instances of the class and call them from python. It is also possible to do the following in my c++ object-code: "ret = boost::python::call<int>(PyFunction.ptr(), this );" But now my problem: boost copies the object and passes only that copy to the function. Is it and how is it possible to make the object accessible to the function within the python-script? I have found some hints in the boost-source for using smartptr but I was unable to use them as an parameter for call(): "TypeError: No to_python (by-value) converter found for C++ type: class boost::shared_ptr<TYPE>". I am also don't known if this is the right way to do. Thanks for help! Marco Borm

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class_, HeldType, and NonCopyable...please help !!
by Stefan Seefeld March 10, 2005

March 10, 2005

hello, I'm trying to wrap an API but having problems at runtime that I can't quite figure out how to resolve. Let me describe the situation: My API deals with pointers referring to objects that are garbage collected. The objects are always created by factories and never directly allocated via 'new'. It thus seemed natural to declare class_<Node, Node *> node("Node", no_init); but this produced an error because of Node having abstract methods. Fair enough. My next attempt was to instruct bpl that 'Node' can't be copied: class_<Node, Node *, boost::noncopyable> node("Node", no_init); That compiles. However, I also have a 'Visitor' class with a 'visit(Node *)' method that I expose, and implement as class VisitorWrapper : public Visitor { public: ... virtual void visit(Node* n) { call_method<void>(self, "visit", n);} ... }; The call to "visit" above, when executed, results in the exception: "TypeError: No to_python (by-value) converter found for C++ type: Node" and here I'm lost. Going back to the documentation I find: NonCopyable If supplied, must be boost::noncopyable. Suppresses automatic registration of to_python conversions which copy T instances. Required when T has no publicly-accessible copy constructor. (on http://boost.org/libs/python/doc/v2/class.html) However, 'T' here is 'Node', not the HeldType 'Node *', and so I wonder how I can a) suppress the need for N's copy-constructor *and* b) have to_python conversions generated for the *HeldType*, i.e. 'Node *'. Can anybody help ? Thanks a lot ! Stefan

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bug: python.hpp not including python/make_constructor.hpp
by Stefan Seefeld March 10, 2005

March 10, 2005

hi, as the subject suggests: including <boost/python.hpp> in my code isn't enough to be able to use 'boost::python::make_constructor()'. #include <boost/python/make_constructor.hpp> somewhere in boost/python.hpp should fix this. Thanks, Stefan

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Sorry for my absence
by David Abrahams March 10, 2005

March 10, 2005

Although I have been busy and didn't intend to be very active here, this list wasn't supposed to drop off my radar. But somehow the newsgroup got deleted from the list in my newsreader. Out of sight, out of mind, as they say. I'll be around, though of course I'm not going to participate in every thread ;-) -- Dave Abrahams Boost Consulting www.boost-consulting.com

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LinkLibraries
by Jacques Kerner March 4, 2005

March 4, 2005

Hello, I am having a problem to link an extension module with bjam, which requires an external library. I get this : Unknown suffix on <@boost!libs!python!example!hlapython>. - see UserObject rule in Jamfile(5). Here is my Jamfile, very close to the basic example, with a <library-file> added to it: # Specify our location in the boost project hierarchy subproject libs/python/example/hlapython ; # Include definitions needed for Python modules import python ; extension hlapython # Declare a Python extension called hlapython : HLAPython.cpp # source <dll>../../build/boost_python # dependencies <library-file>libFedTime <library-file>libRTI-NG ; This is on Windows XP with Visual 7.1 (I don't think it is the problem). I don't understand how to link a library. I also tried : LinkLibrary hlapython : libFedTime libRTI-NG; but it does not work... Any help greatly appreciated. Best Regards, Jacques Kerner

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AttributeError: 'Ipp8uC3ParticleFilter' object has no attribute 'initTrack'
by Michael Zhang March 2, 2005

March 2, 2005

Hello, I have built a model in C with files 'Ipp8uC3ParticleFilter.c' and 'Ipp8uC3ParticleFilter.h'. But when I am trying to load a method "initTrack" I got the following error. Traceback (most recent call last): File "ShowAll_PF.py", line 137, in _threadEntry self.tracker.initTrack(left, top, width, height); AttributeError: 'Ipp8uC3ParticleFilter' object has no attribute 'initTrack' My .c and .h file are created by modifying a sample that works fine. Thanks for you any suggestion, Michael __________________________________ Celebrate Yahoo!'s 10th Birthday! Yahoo! Netrospective: 100 Moments of the Web http://birthday.yahoo.com/netrospective/

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Projects using Boost.Python
by Mustafa Thamer March 2, 2005

March 2, 2005

Games Civilization IV "The fourth game in the PC strategy series that has sold over five million copies, Sid Meier's Civilization IV is a bold step forward for the franchise, with spectacular new 3D graphics and all-new single and multiplayer content. Civilization IV will also set a new standard for user-modification, allowing gamers to create their own add-ons using Python and XML. Sid Meier's Civilization IV will be released for PC in late 2005. For more information please visit www.firaxis.com or write kgilmore(a)firaxis.com." Boost.Python is used as the interface layer between the C++ game code and Python. Python is used for many purposes in the game, including map generation, interface screens, game events, tools, tutorials, etc. Most high-level game operations have been exposed to Python in order to give modders the power they need to customize the game. -Mustafa Thamer Civ4 Lead Programmer

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