Mailman 3 April 2004 - Cplusplus-sig

wchar_t bindings for Boost.Python
by Eric Ries April 2, 2004

April 2, 2004

David Abrahams suggested that I post my message below here, which I mistakenly sent directly to him originally. I am happy to provide source code if there is interest; let me know. Thanks! Eric -----Original Message----- From: David Abrahams [mailto:dave@boost-consulting.com] Sent: Friday, April 2, 2004 08:31 PM To: 'Eric Ries' Subject: Re: [C++-sig] Re: Boost.Python problems "Eric Ries" <ericries(a)speakeasy.net> writes: > Hello, > > I am a brand new Boost.Python user, and I am very impressed. So first > off, thanks for the awesome work that has gone into Boost.Python and > Boost generally. Glad you like it! > I have been using Pyste to generate Boost.Python bindings for C++, and > noticed that there is not automatic support for wchar_t -> py unicode > conversions for C++ functions that return that type. > > While searching for a solution, I came across an email of yours > (http://mail.python.org/pipermail/c++-sig/2003-March/003633.html) in > which you wrote: > >>> 4. There are no converters for std::wstring or wchar_t. >> >>Good point. Care to contribute some? > > So I figured I would give it a try. I was pleasantly surprised by how > easy it was. That probably means that either 1) you guys have already > done this on your development branch (I am on a vanilla 1.31.0 intall) > or 2) my solution was easy because it does not generalize to other > compilers. > > But, on the off chance that it might be useful to you, I wanted to > write and see if you would like me to send in a patch. I modified > Pyste as well as several boost.python hpp files. I have only tested on > MSVC6. First, please in the future always post things like this on the C++-sig. There are other people there who ought to see your post too. We already have wstring converters, but you could contribute converters for wchar_t and I'd be happy to have them. I don't know why you'd have to change Pyste, but that's not my department (another reason to post on the C++-sig). Cheers, -- Dave Abrahams Boost Consulting www.boost-consulting.com

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Re: Accessing instances of C++ objects in Python - Plus more
by Mike Gonzales April 2, 2004

April 2, 2004

Thank you for your input - I am incorporating it to make my code neater and more precise. Anyway, I guess my question devolves to this: How do I access a C++ variable from python, and what steps do I need to take? The most obvious hack that I thought of was to try and manually insert the python-wrapped C++ variable into the main module's namespace dictionary; Is there a better way than that? Thanks for your time and patience, Mike

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Vega Strike uses boost::python
by Daniel Horn April 2, 2004

April 2, 2004

Vega Strike is the 3D Space Simulator that allows you to trade and bounty hunt in a vast universe. Players face dangers, decisions, piracy, and aliens... Instead of going the hackneyed route of using Lua for game scripting, Vega Strike (http://vegastrike.sourceforge.net/) has decided to base its scripting on python, using boost as the layer between the class hierarchy in python and the class hierarchy in C++. The result is a very flexible scripting system that treats units as native python classes when designing missions or writing AI's. A large economic and planetary simulation is currently being run in the background in python and the results are returned back into C++ in the form of various factions' spaceships appearing near worlds that they are simulated to be near in python if the player is in the general neighborhood.

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Pyste: Virtual class wrapper doesn't refcount object
by Dan Halbert April 2, 2004

April 2, 2004

In Pyste from the 1.31.0 release: If Pyste finds any virtual methods in a class it is wrapping (if I understand correctly), it generates a class wrapper for that class that looks something like this: struct VMClass_Wrapper : VMClass_Wrapper { (PyObject* self_): VMClass(), self(self_) {} void f(long int p0) { call_method< void >(self, "f", p0); } PyObject* self; }; Note that the self object is not properly reference-counted. It seems to me it should be, since it's held by the struct, and can disappear from scope in the Python code, and so would go out of existence. I had just such an error when using this class in a callback situation: registerMyCallback(VMClass(), ...) # uses an anonymous VMClass() object I fixed this by modifying the code generated by Pyste to use handle<> and borrowed(): struct VMClass_Wrapper : VMClass_Wrapper { (PyObject* self_): VMClass(), self(borrowed(self_)) {} // was self(self_) void f(long int p0) { call_method< void >(self.get(), "f", p0); // was just self } handle<> self; // was PyObject* self; }; Anything wrong with this? I believe I am using borrowed() properly here, but I'm not 100% sure. If it's OK, it's a fix to make to Pyste. Dan

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missing symbol in boost_python 1.31
by Stefan Seefeld April 1, 2004

April 1, 2004

hi there, I'v switched from boost.python 1.30.2 to 1.31 yesterday, and I'm getting a runtime error concerning a missing symbol boost::python::objects::function_object(boost::function2<_object*, _object*, _object*, std::allocator<boost::function_base> > const&, unsigned) I'm working with g++ 3.2 on a RH 8 system. Any ideas what could cause this ? I didn't make any changes to my code... Thanks, Stefan

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