Mailman 3 April 2004 - Cplusplus-sig

how to get python expection infomation in c++?
by iceryeah April 8, 2004

April 8, 2004

hello, if python script has error when c++ prog is running, i can get the expection with error_already_set, now i want to get the expection infomation, but python interpreter output info to std_err, i can't get it! tell me your method how to get expection info. thanks

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Re: [C++-sig] Re: how to get python expection infomation in c++?
by Paul Grenyer April 8, 2004

April 8, 2004

Hi > Easier approaches are detailed here: > > http://tinyurl.com/uiis > > and in: > > http://tinyurl.com/uiiu Which is great if you have a console for std::err to display the error on. If, like us, you've embedded python in a GUI based app, this doesn't work. Correct me if I'm wrong??? Regards Paul Paul Grenyer Email: paul(a)paulgrenyer.co.uk Web: http://www.paulgrenyer.co.uk Have you met Aeryn: http://www.paulgrenyer.co.uk/aeryn/? Version 0.3.0 beta now available for download.

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problems with compiling and loading C++ extension
by Faheem Mitha April 8, 2004

April 8, 2004

Dear People, I have been having an odd problem with compiling and loading a simple C++ extension to python (as a .so file in Linux). Unfortunately, I'll need to include my files in here so I apologize in advance for the length of this message. You can download also the files below from http://www.stat.unc.edu/students/faheem/python/python.tar.gz in case that is more convenient. When I try to load arrmod.so into python I get In [1]: import arrmod --------------------------------------------------------------------------- ImportError Traceback (most recent call last) /tmp/wc/corrmodel/ex/<console> ImportError: ./arrmod.so: undefined symbol: _Z11py_to_blitzIdLi2EEN5blitz5ArrayIT_XT0_EEEP13PyArrayObject If I move the py_to_blitz routine from conv.cc back into arrmod.cc, the error disappears, arrmod loads in python, and everything works correctly. I'm not sure what is going on here. Can someone enlighten me? At first I thought it might have to do with the need for C linkage, but I tried that, and it does not appear to be the case. I also got the following compilation warning, which I don't understand. I don't know if that is relevant. --------------------------------------------------------------------- gcc -pthread -fno-strict-aliasing -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.3 -c conv.cc -o /tmp/temp.linux-i686-2.3/conv.o -Wall /usr/include/python2.3/Numeric/arrayobject.h:286: warning: `void**PyArray_API' defined but not used --------------------------------------------------------------------- Thanks in advance for any enlightenment. Faheem. ********************************************************************** Makefile ********************************************************************** arrmod.so: arrmod.cc common.hh conv.cc python setup.py build --build-base=/tmp --build-lib=. # may not do the right thing for everyone clean: rm arrmod.so rm -r /tmp/temp.linux-i686-2.3 ********************************************************************** ********************************************************************** setup.py ********************************************************************** from distutils.core import setup, Extension module4 = Extension('arrmod', sources = ['arrmod.cc','conv.cc'],libraries=["blitz","m"], extra_compile_args = ['-Wall']) setup (name = 'arrmod', version = '1.0', description = 'This module performs different operations on arrays', ext_modules = [module4] ) ********************************************************************** ********************************************************************** common.hh ********************************************************************** #include "Python.h" #include "Numeric/arrayobject.h" #include <blitz/array.h> using namespace std; using namespace blitz; template<class T, int N> static Array<T,N> py_to_blitz(PyArrayObject* arr_obj); ********************************************************************** ********************************************************************** conv.cc ********************************************************************** #include "common.hh" // Convert a Numpy array to a blitz one, using the original's data (no // copy) template<class T, int N> static Array<T,N> py_to_blitz(PyArrayObject* arr_obj) { int T_size = sizeof(T); TinyVector<int,N> shape(0); TinyVector<int,N> strides(0); int *arr_dimensions = arr_obj->dimensions; int *arr_strides = arr_obj->strides; for (int i=0;i<N;++i) { shape[i] = arr_dimensions[i]; strides[i] = arr_strides[i]/T_size; } return Array<T,N>((T*) arr_obj->data,shape,strides,neverDeleteData); } ************************************************************************ ************************************************************************ arrmod.cc ************************************************************************ #include "common.hh" template<class T, int N> static Array<T,N> py_to_blitz(PyArrayObject* arr_obj); static PyObject * arrmod_elem(PyObject *self, PyObject *args); static PyMethodDef arrmod_methods[] = { {"elem", (PyCFunction)arrmod_elem, METH_VARARGS, "Returns the trace of a two-dimensional array.\n"}, {NULL, NULL, 0, NULL} }; PyMODINIT_FUNC initarrmod(void) { (void) Py_InitModule3("arrmod", arrmod_methods, "Returns the Trace of a two-dimensional array.\n"); import_array(); } static PyObject * arrmod_elem(PyObject *self, PyObject *args) { PyObject *input, *result; PyArrayObject *array; double el; int i, j; if (!PyArg_ParseTuple(args, "Oii", &input, &i, &j)) return NULL; array = (PyArrayObject *) PyArray_ContiguousFromObject(input, PyArray_DOUBLE, 2, 2); if (array == NULL) return NULL; Array<double,2> arr = py_to_blitz<double,2>(array); el = arr(i,j); result = Py_BuildValue("d",el); return result; } ********************************************************************************

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RE: [C++-sig] VC6 Compile error with boost 1.31.0
by Peter April 8, 2004

April 8, 2004

Thanks Eric, it builds ok now. Hoepefully that bit of code isn't critical for anything. Peter > I can't claim this is anything but a hack, but I was able to work around > this problem with no ill effects with a handy #if 0: > > in boost\graph\detail\adjacency_list.hpp:1047 > > #if 0 > // O(E/V) or O(log(E/V)) > template <class Config> > inline void > bidirectional_graph_helper_with_property<Config>::remove_edge(typename > Config::edge_descriptor e) > { > typedef typename Config::graph_type graph_type; > graph_type& g = static_cast<graph_type&>(*this); > boost::remove_edge(source(e, g), target(e, g), *this); > } > #endif > > I'm still able to build the boost_python dll with MSVC6 and build various > python extension DLLs. > > Hope that is helpful... > > Eric > > >

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VC6 Compile error with boost 1.31.0
by Your Name April 7, 2004

April 7, 2004

Using VC6, Python 2.3 and Boost 1.31.0, I get the following errors inheritance.cpp C:\Lib\boost_1_31_0\boost/graph/detail/adjacency_list.hpp(1055) : error C2244: 'bidirectional_graph_ move_edge' : unable to resolve function overload C:\Lib\boost_1_31_0\boost/graph/detail/adjacency_list.hpp(1057) : error C2954: template definitions plus a whole lot more. I know others have had this problem, and the only answer I saw was to get a snapshot direct from CVS. Sadly I can't get direct CVS access from my location. Is there anywhere else I can get an update to the specific files? And can someone list which files I need to get to fix this? Thanks. Peter

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boost-python + lambda
by Neal D. Becker April 7, 2004

April 7, 2004

I'd like to wrap a class, but with a modified interface to some member functions. The easy way is write c++ code to wrap the class, inherit from it, and add the new member function, then expose that. I wonder if lambda can be used as a more direct approach? If so, what would the syntax look like? struct A { some_function (sig1); }; BOOST_PYTHON_MODULE (Test2) { class_<A> ("A") .def(some_function2 ( insert lambda here? )

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Reinitialization of interpreter with Boost.Python
by Maciej Sobczak April 7, 2004

April 7, 2004

Hi, I use Boost.Python (from 1.30.2 release) for interpreter embedding. The idea is to run short, customized scripts from within the C++ application and have the scripts operate on application's data structures. My use of Python interpreter is tightly scoped and what I need is the possibility to *repeatedly* do the following: 1. initialize the interpreter 2. import module defined in the application's code 3. execute some Python script 4. finalize the interpreter The problem is that the second time (after the interpreter is re-initialized) my module is imported, the code that defines classes cannot go past the registration procedure. This is due to the fact that the slots for conversion functions cannot be reused and the code stumbles either on assertion (in Debug build) or the exception is thrown (in Release build). The "offending" code is in the converter/registry.cpp file (of Boost.Python): void insert(to_python_function_t f, type_info source_t) { # ifdef BOOST_PYTHON_TRACE_REGISTRY std::cout << "inserting to_python " << source_t << "\n"; # endif to_python_function_t& slot = get(source_t)->m_to_python; assert(slot == 0); // we have a problem otherwise if (slot != 0) { throw std::runtime_error( "trying to register to_python_converter for a type which already has a registered to_python_converter"); } slot = f; } Considering the fact that what I need is the possibility to reinitialize the interpreter in exactly the same manner, importing the same module that defines the same classes - the second time the module is imported, the converion function is exactly the same. I have hacked the above function and removed both assertion and if, so that the conversion function pointer is always written into the slot. The second time my module is imported (after the interpreter is finalized and re-initialized), the insert function above will just overwrite the slot with the same value as before. Interestingly, it started to work as expected, at least with simple tests. What bothers me is the claim I found on Boost site, that reinitialization of Python interpreter is *not* supported due to the reference-counting problems affecting some global objects. I do not experience any problems *at the moment*, but I would like to know where the trolls may come from. What is exactly the problem? What should I be aware of? Thank you very much for your time, -- Maciej Sobczak : http://www.msobczak.com/ Programming : http://www.msobczak.com/prog/

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VC6 Compile error with boost 1.31.0
by Your Name April 7, 2004

April 7, 2004

Using VC6, Python 2.3 and Boost 1.31.0, I get the following errors inheritance.cpp C:\Lib\boost_1_31_0\boost/graph/detail/adjacency_list.hpp(1055) : error C2244: 'bidirectional_graph_ move_edge' : unable to resolve function overload C:\Lib\boost_1_31_0\boost/graph/detail/adjacency_list.hpp(1057) : error C2954: template definitions plus a whole lot more. I know others have had this problem, and the only answer I saw was to get a snapshot direct from CVS. Sadly I can't get direct CVS access from my location. Is there anywhere else I can get an update to the specific files? And can someone list which files I need to get to fix this? Thanks. Peter

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blitz++ and numarray
by Faheem Mitha April 7, 2004

April 7, 2004

Hi, I'm considering the use of the Blitz++ C++ library (http://www.oonumerics.org/blitz/) along with numarray/Numeric. I want to pass an array down to C++ and then manipulate it using Blitz++. My current thinking is to use the Numeric interface to pass down the array, and then copy it to a blitz++ array object. This seems straightforward except I am a little concerned about those reference counting issues, which I don't properly understand (I'm a Python beginner). I do get the impression that it is mainly an issue if I am working with Python objects in C/C++ code, though, and I am mostly going to try to avoid doing so by declaring C++ objects within the C++ code and working with those as much as possible. Other possibilities include somehow using the Boost.Python package, though I am not sure how. One advantage of this is that it apparently takes care of the reference counting issue. However, I don't want to learn yet another API. Also, weave.blitz() from SciPy looks relevant/useful, but this automatically generates its own C++ code, and I'd prefer to write my own. Can anyone suggested a good basic tutorial which discusses the issues of reference counting in a C/C++ API context? I have tried reading the official documentation and will continue to do so, but something gentler would be useful. Comments, suggestions gratefully appreciated. Please cc me on any reply to faheem(a)email.unc.edu. Thanks in advance. Faheem.

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Pyste and exporting inherited items
by Niall Douglas April 6, 2004

April 6, 2004

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Bruno, are you aware that by adding the exporters.importing mechanism you have totally broken pyste's detection of class inheritance thus causing the class_<...bases<base> > system to stop working? Furthermore nested class definitions get replicated, thus causing Boost.Python to fault on startup complaining about multiple definitions. The solution for others afflicted is to comment out line 55 "if not exporters.importing" in infos.py. Cheers, Niall -----BEGIN PGP SIGNATURE----- Version: idw's PGP-Frontend 4.9.6.1 / 9-2003 + PGP 8.0.2 iQA/AwUBQGvxR8EcvDLFGKbPEQKKxwCfRBndMv7ZIShBeodqkLHz/nToXPEAoK4U VoWQoNIhxixjreYHL6vmkUds =JYuC -----END PGP SIGNATURE-----

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