Mailman 3 October 2009 - Cplusplus-sig

[Urgent Question] Import Qt builded Lib into python with Boost.python
by Cheng Lee Oct. 10, 2009

Oct. 10, 2009

Hello All, Our project made some of the functions with Qt and also encapsulate them with dll library, the imported module, we made it following the boost.python syntax, was built successfully, and imported into python 2.6.2 with no errors, but our issues are, the functions donot work, no response as our investigation, it supposes to be Qt signal/slot donot work in the python module I made a simple example below: Would someone help me check what codes i need add to make the signal/slot work in the python, Thanks a lot Boost 1.40 Python 2.6.2 ++++++++++++++++++++++++++++++++++++++++++++++++++.h #ifndef SIGALE_H #define SIGALE_H #include<QObject> class SignalMine : public QObject { Q_OBJECT public: SignalMine(QObject* parent = 0); void submit(void){emit trigger();} signals: void trigger(void); protected slots: void printOut(void); }; #endif ++++++++++++++++++++++++++++++++++++++++++++++++++.cpp #include<iostream.h> #include"example.h" SignalMine::SignalMine(QObject* parent):QObject(parent) { connect(this, SIGNAL(trigger()), this, SLOT(printOut())); } void SignalMine::printOut() { cout << "Get signal!" << endl; } //! for boost.python #include <boost/python.hpp> using namespace boost::python; BOOST_PYTHON_MODULE(SIGN) { class_<QObject, boost::noncopyable>("QObject"); class_<SignalMine, boost::noncopyable, bases<QObject>>("SignalMineller") .def("submit", &SignalMine::submit); } _________________________________________________________________ Keep your friends updated―even when you’re not signed in. http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/so…

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"pass all args in list" syntax
by Gennadiy Rozental Oct. 9, 2009

Oct. 9, 2009

Hi, In native Python I can do something like this: def goo(a,b,c): return a+b+c ll = [1,2,3] goo( *ll ) And it will pass all the arguments properly. I need similar functionality in C++: Given bp::object func; bp::list args; I'd like to invoke the function like this func( *args ); Is there syntax in Boost.Python to achieve this? Or I need to resort to ugly switch statement? Gennadiy

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call_method crash
by Gustavo Adolfo Borges Oct. 8, 2009

Oct. 8, 2009

Since Python Win32 lib does not implement DDE Advise Loop and i need it for a project, i guessed that Boost Python would be a way to integrate the ddeml lib with my python code. I guessed i could just call call_method inside the DDE Callback function, but when i do that python crashes. I can't(or couldnt find how to) add the DDE Callback function to the Python Module and i tried through a 2 stages call(DdeCallback calls a Python Module function that call_method) without success. Everything else works great... I can connect to the DDE Server, the advise loop works, my setPyCallback/getPyCallback works... I just can't get any python to work on the C++ DDECallback function. Here is part of the code ------------------ PyObject* myPythonCallback; void CallPy(TCHAR SomeValue){ boost::python::call<void>(myPythonCallback,SomeValue); } HDDEDATA CALLBACK DdeCallback(UINT wType,UINT uFmt,HCONV hconv,HSZ hsz1,HSZ hsz2,HDDEDATA hData,DWORD dwData1,DWORD dwData2){ .......... switch (wType) { case XTYP_ADVDATA: .................. bunch of code .......... CallPy(mybuffer); return((HDDEDATA)DDE_FACK); } int ddeConnect(); void ddeAdvise(TCHAR* topic); void setCallback(PyObject* p){ boost::python::call<void>(p,"3");// test calling function and WORKS myPythonCallback = p; } BOOST_PYTHON_MODULE(extending) { using namespace boost::python; def("ddeConnect", ddeConnect); def("ddeAdvise", ddeAdvise); def("ddeSetCallback", setCallback); def("CallPy", CallPy); } ------------- Python ------------ import extending import wx import justAFrame def mCB (valor): print "mCB",str(valor) return float(str(valor)) class MyFrame(justAFrame.MyFrame): def initAfter (self): justAFrame.MyFrame.initAfter(self) extending.ddeConnect() extending.ddeSetCallback(mCB) extending.CallPy("1") #WORKS extending.ddeAdvise("0012PETR4;1") app = wx.PySimpleApp() frame=MyFrame(None,title="DDE Test") app.MainLoop() -------------- How can i make this DdeCallback to interact with a python function defined by the user ? Is there a better way to do this ? I'm open to suggestions.

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Setting up a boost.python workflow on a Mac
by Randolph Fritz Oct. 4, 2009

Oct. 4, 2009

I have just successfully--I hope--done this & I want to get my notes down before I forget the problems I encountered. These occurred with Boost 1.39 and Mac OS 10.5.8. 1. Bjam did not automatically detect the Mac OS environment and compilation consistently failed. So, I added the following line to /etc/site-config.jam: using darwin ; 2. I built boost.python according to the getting started guide. This left me with four files in stage/bin: libboost_python-xgcc40-mt-1_39.a libboost_python-xgcc40-mt-1_39.dylib libboost_python-xgcc40-mt.a libboost_python-xgcc40-mt.dylib 3. The install command recommended by bjam was "bjam install --prefix=<place>". I attempted to use the command, and found it consistently tried to place files in /lib. A manual move to my target library directory fixed that problem. 4. It turned out that the default build script automatically looked for debug libraries, which weren't automatically built. I tried "bjam debug" and it placed the following four files in stage/bin: libboost_python-xgcc40-mt-d-1_39.a libboost_python-xgcc40-mt-d-1_39.dylib libboost_python-xgcc40-mt-d.a libboost_python-xgcc40-mt-d.dylib These I also placed manually. 5. I then discovered that the sample Jamroot provided did not support multi-threaded (*-mt-*) libraries. I added the following symbolic links to my target directory: libboost_python-xgcc40-1.39.dylib -> libboost_python-xgcc40-mt-1_39.dylib libboost_python-xgcc40-d-1_39.dylib -> libboost_python-xgcc40-mt-d-1_39.dylib 6. Voila! My test application built and apparently ran. -- Randolph Fritz design machine group, architecture department, university of washington rfritz(a)u.washington.edu -or- rfritz333(a)gmail.com

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Conversion from Python to C++
by Michele De Stefano Oct. 2, 2009

Oct. 2, 2009

Hello to everybody. I was wondering if there is a general way to convert a C++ class wrapped in Python into a C++ class not wrapped in Python. I've not fully understood the documentation on this point. For example, assume we have two C++ classes, A and B. A is exported to Python with class_<>, while B is not exported to Python. Assume also that, in C++, A is convertible to B (i.e. I can construct a B object from an existing A object). Assume I have a C++ function (f) which takes a B object as input and I want to expose this function, but I don't want to expose the B class. Is there a general way to create a converter from A to B in order to be able to call f(A) from Python ? Thank you in advance. -- Michele De Stefano

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Re: [C++-sig] [Py++] Does pyplusplus respect explicit constructors?
by Christopher Bruns Oct. 1, 2009

Oct. 1, 2009

Roman Yakovenko wrote: > On Wed, Sep 30, 2009 at 6:18 PM, Christopher Bruns <cmbruns at stanford.edu> wrote: > > I suspect I can manually adjust the implicitly_convertible tag > > generation using the "allow_implicit_conversion" flag in pyplusplus. > > Is there a way to tell pyplusplus to avoid generating an > > implicitly_convertible tag for all explicit constructors? > > I don't think so. I attached gccxml generated file for your code. As > you can see both constructors ( Foo and Bar ) have "explitic=1". So > Py++ has no way to find out whether a constructor explicit or not. I disagree. Py++ does have a way to find out. The only time "explicit" matters is when a constructor takes exactly one argument. gccxml sets "explicit=1" in all cases when the number of arguments is other than 1. That is why you saw "explicit=1" in all of the constructors in the previous example. However, in the case where there is exactly one argument, gccxml does the right thing. Consider the following case: ### test.h #### struct Foo1 {}; struct Foo2 {}; struct Bar { explicit Bar(Foo1&); // no implicit conversion Bar(Foo2&); // allows implicit conversion }; ############# ### fragment of resulting xml file from gccxml ### <Constructor id="_10" name="Bar" explicit="1" context="_3" access="public" mangled="_ZN3BarC1ER4Foo1 *INTERNAL* " demangled="Bar::Bar(Foo1&)" location="f0:5" file="f0" line="5" extern="1"> <Argument type="_22" location="f0:5" file="f0" line="5"/> </Constructor> <Constructor id="_11" name="Bar" context="_3" access="public" mangled="_ZN3BarC1ER4Foo2 *INTERNAL* " demangled="Bar::Bar(Foo2&)" location="f0:6" file="f0" line="6" extern="1"> <Argument type="_23" location="f0:6" file="f0" line="6"/> </Constructor> ####################### Notice that gccxml sets "explicit=1" for the first Bar constructor, but not for the second. However, Py++ sets "allow_implicit_conversion" to True for both constructors. I think gccxml is doing the right thing here. But I am not so sure about Py++ behavior. I would have assumed that the first Bar constructor would have "allow_implicit_conversion" set to False. I was wrong about being able to use "allow_implicit_conversion" for this task. Is there another way to get at the "explicit" xml tag from the module_builder object? Or do I need to parse the xml file or source code separately to discover this information? Thank you Roman for your diligent feedback. I sincerely appreciate the quick and thoughtful feedback you provide to everyone on this mailing list. Chris Bruns

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boost python to/from python type conversion
by James Amundson Oct. 1, 2009

Oct. 1, 2009

Hi, I'm trying to write to/from type converters for my code, and I'm stuck. My case doesn't map well to any of those in the boost python documentation. I'm trying to pass objects of type MPI_Comm (really a C type!) back and forth with mpi4py (which uses cython internally.) The mpi4py author has provided a working example using manual wrapping. I am attaching it to the end of this message. On the C++ side I can extract a point to the MPI_Comm object from a Python object like so: PyObject* py_obj; // obviously, the value of py_obj has to be set somewhere... MPI_Comm *comm_p = PyMPIComm_Get(py_obj); I thought it would be simple to write a type converter to do that, but I don't understand the mechanics. This example doesn't seem to map onto the lvalue_from_pytype paradigm, or the scitbx container_conversion paradigm. Any suggestions? Thanks, Jim Amundson ----------------------------------- // working example with manual conversion #include <mpi.h> #include <iostream> static void sayhello(MPI_Comm comm) { if (comm == MPI_COMM_NULL) { std::cout << "You passed MPI_COMM_NULL !!!" << std::endl; return; } int size; MPI_Comm_size(comm, &size); int rank; MPI_Comm_rank(comm, &rank); int plen; char pname[MPI_MAX_PROCESSOR_NAME]; MPI_Get_processor_name(pname, &plen); std::cout << "Hello, World! " << "I am process " << rank << " of " << size << " on " << pname << "." << std::endl; } #include <boost/python.hpp> #include <mpi4py/mpi4py.h> using namespace boost::python; static void hw_sayhello(object py_comm) { PyObject* py_obj = py_comm.ptr(); MPI_Comm *comm_p = PyMPIComm_Get(py_obj); if (comm_p == NULL) throw_error_already_set(); sayhello(*comm_p); } BOOST_PYTHON_MODULE(helloworld) { if (import_mpi4py() < 0) return; /* Python 2.X */ def("sayhello", hw_sayhello); }

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[Py++] Does pyplusplus respect explicit constructors?
by Christopher Bruns Oct. 1, 2009

Oct. 1, 2009

Single-argument C++ constructors in pyplusplus seem to generate a boost::python::implicitly_convertible tag, even when the constructor is declared "explicit" in C++. That doesn't sound right to me. Shouldn't a pair of types that are not implicitly convertible in C++, also not be implicitly convertible in python? I suspect I can manually adjust the implicitly_convertible tag generation using the "allow_implicit_conversion" flag in pyplusplus. Is there a way to tell pyplusplus to avoid generating an implicitly_convertible tag for all explicit constructors? ########## test.h input source ############ class Foo { public: Foo() {} }; class Bar { public: // explicit constructor means don't implicitly convert Foo to Bar in C++ explicit Bar(Foo&) {} }; ############################### ########## wrap.py wrapping code #### from pyplusplus import module_builder mb = module_builder.module_builder_t(["test.h"] , gccxml_path = "C:\\Program Files\\gccxml_sherm\\bin\\gccxml.exe") mb.build_code_creator( module_name='test' ) mb.write_module( 'test_explicit.cpp' ) ################################## ##### generated test_explicit.cpp ###### // This file has been generated by Py++. #include "boost/python.hpp" #include "test.h" namespace bp = boost::python; BOOST_PYTHON_MODULE(test){ { //::Bar typedef bp::class_< Bar > Bar_exposer_t; Bar_exposer_t Bar_exposer = Bar_exposer_t( "Bar", bp::init< Foo & >(( bp::arg("arg0") )) ); bp::scope Bar_scope( Bar_exposer ); bp::implicitly_convertible< Foo &, Bar >(); // <-- *** I'm surprised by this *** } bp::class_< Foo >( "Foo", bp::init< >() ); } ##################################

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