Mailman 3 August 2004 - Cplusplus-sig

Wrapped shared_ptr's
by James Mastro Aug. 9, 2004

Aug. 9, 2004

Well, I have C++ and Python working together happily for my basic types. How do I go about wrapping shared_ptr's, though? My C++ code doesn't pass around any raw ptr's, just shared_ptr's. So I have a class called ObjectPtr: class Object { public: Object() {} void setData( int data ) { mData = data; } private: int mData; }; typedef boost::shared_ptr<Object> ObjectPtr; Right now this works fine with Python if I'm just passing the object back and forth. But I want to call Object's functions from Python. What I have now is just this: BOOST_PYTHON_MODULE( MyModule ) { class_< ObjectPtr>( "Object", init<>() ) .def( "setData", &Object::setData ) ; } which is of course incorrect. Is register_ptr_to_python required here? -jim

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Exposing C++ Class instances to Python
by xin Aug. 7, 2004

Aug. 7, 2004

So I have the following code. /***** START Point.cpp *****/ struct Point { Point() { count = 0; size = 1; script="testScript"} int count; int size; char *script; }; BOOST_PYTHON_MODULE(HgSharedLib) { class_<Point>("Point") .def_readonly("count", &Point::count) .def_readwrite("size", &Point::size); } /***** END Point.cpp *****/ /***** START PyController.cpp ******/ PyObject *pyController::getPyFunc(char *moduleName, char *functionName) { /* Courtsey of Jeffrey Holle */ PyObject *pModule = PyImport_ImportModule(moduleName); if(pModule == NULL) std::cout << "The Python Module \"" << moduleName << "\" is not available" << std::endl; PyObject *pDict = PyModule_GetDict(pModule); if(pDict == NULL) std::cout << "Failed to Aqquire dictionary of \"" << moduleName << "\"" << std::endl; PyObject *pFunc = PyDict_GetItemString(pDict,functionName); if(pFunc == NULL) std::cout << "Failed to find requested python function \"" << functionName << "\"" << std::endl; Py_DECREF(pModule); return pFunc; } bool pyController::runScript(Point &dest) { Py_Initialize(); PyRun_SimpleString("import sys\nsys.path.append(\"/home/xin/code/Hg/src\")"); PyObject *pFunc = getPyFunc(dest.script, "TestFunc"); std::cout << "Start Size: " << dest.size << std::endl; // Run TestFunc Here std::cout << "End Size: " << dest.size << std::endl; Py_Finalize(); } /***** END PyController.cpp *****/ /**** START main.cpp *****/ int main() { Point foo; pyController PyCon; PyCon.runScript(foo); return 0 } /**** END main.cpp *****/ /***** START testScript.py *****/ def TestFunc (pt): pt.size = 5 return pt.size /***** END testScript.py *****/ My overall goal is to run TestFunc on foo. And the output to end up like. Start Size: 1 End Size: 5 What Im unsure of, is how to turn foo into a PyObject to then run the python FUnction TestFunc with the new PyObject (foo) as an arguement. ( Python Equiv: TestFunc(foo) ) I hope Im making sense.. Thanks for you help

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numarray, lvalue_from_pytype
by Neal D. Becker Aug. 6, 2004

Aug. 6, 2004

I'm trying to write some c++ functions to be interfaced with numarray. I ran into this: TypeError: No registered converter was able to extract a C++ reference to type s_PyArrayObject from this Python object of type NumArray I thought I'd use lvalue_from_pytype like this: lvalue_from_pytype<extract_identity<s_PyArrayObject>, &_numarray_type>(); Problem is, _numarray_type is declared static, so the symbol is not visible. In fact, this is right out of the model python type extension code, so it would typically be the case that the PyTypeObject is static in the defining module. Any suggestions?

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RE: [C++-sig] Re: add_property and boost::bind?
by Max Khesin Aug. 5, 2004

Aug. 5, 2004

awsome, it woiks! Thanks, Dave, Daniel. m > -----Original Message----- > From: Daniel Wallin [mailto:dalwan01@student.umu.se] > Sent: Thursday, August 05, 2004 4:52 AM > To: c++-sig(a)python.org > Subject: [C++-sig] Re: add_property and boost::bind? > > > Max Khesin wrote: > >>You can use make_function with a Signature parameter and > pass that to > >>add_property. But your bind expression above won't work. > >> > >>Maybe something like: > >> > >> .add_property("aaa", > >> make_function( > >> boost::bind(&Foo::lookup, _1, "aaa") > >> , default_call_policies() > >> , mpl::vector1<int>() > >> ) > >> ) > >> > > > > > > This is what I was looking for. I knew my example was not > complete - it was > > just wishful thinking code. But this fails to compile on > vc6 & vc8, both > > pretty much indicate the same error: > > c:\home\mkhesin\libs\boost_1_31_0\boost\bind.hpp(246) : error C2784: > > 'result_traits<R,F>::type boost::_bi::list0::operator [](const > > boost::_bi::bind_t<R,F,L> &) const' : could not deduce > template argument for > > 'const boost::_bi::bind_t<R,F,L> &' from 'boost::arg<I>' > > with > > [ > > I=1 > > ] > > > > any idea? > > I think the signature is supposed to be: > > mpl::vector2<int, Foo&> > > The make_function() call above will create a nullary > function, where _1 > doesn't make any sense. > > HTH, > -- > Daniel Wallin > > _______________________________________________ > C++-sig mailing list > C++-sig(a)python.org > http://mail.python.org/mailman/listinfo/c++-sig > This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail.

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RE: [C++-sig] Re: add_property and boost::bind?
by Max Khesin Aug. 5, 2004

Aug. 5, 2004

> You can use make_function with a Signature parameter and pass that to > add_property. But your bind expression above won't work. > > Maybe something like: > > .add_property("aaa", > make_function( > boost::bind(&Foo::lookup, _1, "aaa") > , default_call_policies() > , mpl::vector1<int>() > ) > ) > This is what I was looking for. I knew my example was not complete - it was just wishful thinking code. But this fails to compile on vc6 & vc8, both pretty much indicate the same error: c:\home\mkhesin\libs\boost_1_31_0\boost\bind.hpp(246) : error C2784: 'result_traits<R,F>::type boost::_bi::list0::operator [](const boost::_bi::bind_t<R,F,L> &) const' : could not deduce template argument for 'const boost::_bi::bind_t<R,F,L> &' from 'boost::arg<I>' with [ I=1 ] any idea? This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail.

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add_property and boost::bind?
by Max Khesin Aug. 4, 2004

Aug. 4, 2004

Is it possible to define a property using boost::python and pass it a boost::bind object instead of a function pointer? e.g something like struct Foo { int lookup(const char*); }; class_<Foo>("Foo") .add_property("aaa", boost::bind(&Foo::lookup, "aaa")) ; This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail.

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Numeric--factory function
by Li Dongfeng Aug. 4, 2004

Aug. 4, 2004

Hi, I'm trying boost python with the python numarray module. The objective is to do something in C++ arrays and be able to transmit input and output with python using numarray.array. I tried to compile the test files numpy.cpp in the python test directory, mostly it goes well, but I found that the ``factory'' function call cause errors when testing from python. Here are the error messages: >>> exercise_numarray(x, p) Traceback (most recent call last): File "<stdin>", line 1, in ? AttributeError: 'NumArray' object has no attribute 'array' where x is an numarray.array, browsing the definition from boost python source file ``numeric.cpp'', I found that the ``factory'' function is a method of class ``array_base'', and it just calls the attr("array") to get the ``array'' method from the underlying python numarray.array object. But I found that the python array has no method named ``array''(it is the ``array'' class name, not a *method* of the numarray.array class). In fact, I found that the python numarray.array class has a ``factory'' method. Am I on some error or is the implementation of boost::python::numeric::array_base::factory not compatible with recent python numarray module(I'm using version 1.0)? Another question: how to convert data in a python numarray.array in C++ to/from raw C++ arrays? Using the xnumarray[make_tuple(2,1)]=ycarray[2*ydim2 + 1] like method should be very in-efficient. Hope someone could enlighten me. Please reply to my email in addition to the sig. 　　　　　　　　Li Dongfeng 　　　　　　　　ldfwyn(a)163.com 　　　　　　　　　　2004-08-04

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pycxx, sequences, stl
by Neal Becker Aug. 3, 2004

Aug. 3, 2004

I am experimenting with pycxx. I want to expose STL vector for high-performance c++ algorithms. The idea is to 1) create vectors in python, 2) call C++ algorithms using them. One problem so far, it looks like we have SeqBase<T>, but T has to be a python object. It looks like we can't have SeqBase<double> for example. So we could make SeqBase<Py::Float>. This is no good for my purpose. I want my sequences to be compact and fast - just wrap std::vector<double>, for example. Any ideas?

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