Mailman 3 July 2003 - Cplusplus-sig

RE: [C++-sig] Re: Wrapper for exception translation
by Gottfried.Ganssauge＠HAUFE.DE Dec. 13, 2004

Dec. 13, 2004

> > ... > >> > >> > Currently, in order to wrap user defined exceptions you need to > >> > > >> > - allocate a python exception using PyErr_NewException > >> > >> Well, no. I don't see any call to PyErr_NewException in > >> libs/python/test/exception_translator.cpp > > > > Right, you don't need to if you are content with RuntimeError > > exceptions. > > or any other pre-packaged exception type provided by Python. > > > My objective was another one: I wanted to create module exceptions > > that are derived from the python "Exception" class. > >> > >> > This function needs to be parametrized using a specific naming > >> > convention > >> > >> It's not clear to me what you're referring to. Are you > sure you mean > >> "naming convention"? > > Yes. > > From the documentation to PyErr_NewException: > > > > ... The __module__ attribute of the new class is set to > the first part > > (up to the last dot) of the name argument, and the > class name is set to > > the last part (after the last dot). > > ...yeah, that's a naming convention, but I don't see how that affects > the parameterization of any function. It is enforced by PyErr_NewException, so you must follow this convention. On the hand I don't think that any user of boost.python is aware of that convention, so I wanted to codify it within my facility. ... > > What I wanted to achieve was the following: > > Create an instance of a translated_exception_handler<> t > which will be > > registered with the library by calling > > register_exception_translator<>(). > > Sorry to be difficult, but I'm going to contradict you. You didn't > want any of that. What you wanted was to create a new Python > exception type in the module which would correspond to a particular > C++ exception type and would be raised at the boundary with Python > whenever a wrapped function threw the C++ exception. Right? Right. I actually described the way to do it within the current library design. > > > Normally t would be destructed by the end of exception_<>() thereby > > leaving a registration to a non-existing translator - very bad > > karma. > > I don't understand any of this. All you have to pass to > register_exception_translator is a function pointer, and functions > live forever. So where's the lifetime issue? A pointer to a function which has access to python exception instance e. As I didn't want to create separate entities I chose to supply a functor instead which has e as a member variable. > > > Because I didn't like to have an additional container for all > > translated_exception_handler<> instances, I chose to store t within > > e's class dictionary. At that moment it seemed to be the easiest > > way to create a wrapper class using class_<> instead of making a > > true python class by hand (and it even works!). You are right, it > > is way too complex, I will change it to the mechanism I used in > > opaque_pointer_converter. > > I don't know what that is, but before you consider doing something > which is again too complex, please consider: > > template <class E> > struct translate_exception > { > static char const* msg; This would need to be defined somewhere. > static object python_exception_type; ... and this would need to be defined somewhere as well. > > static void handler(E const&) > { > PyErr_SetString(python_exception_type.ptr(), msg.c_str()); > }; > > translate_exception(char const* python_exception_name, > char const* msg_) > { > // need fancier name manipulation here > python_exception_type > = object( > handle<>(PyErr_NewException(name))); > msg = msg_; > register_exception_translator<E>(handler); > } > }; > > > Simple. Yes. ... > > I'll make a redesign ... At times you don't see the forrest, just trees ... I think this time I have a simple facility which is also easy to use (no macros). It could be even simpler with a completely different design but frankly - I have no clue how to implement that: We would need a way to somehow derive (in the python sense) a class_<> from PyExc_Exception (the type of the python Exception class) or any other python class (PyErr_NewException() has a base parameter, which could be used for that). At the same time an exception_translator should be registered for that class_<> which uses PyErr_SetObject() to raise a copy of the exception caught. This would allow us to have true Python exceptions in a pythonic sense directly wrapped around the corresponding C++ exception. > > Thnx for your feedback. > > Cool! Looking forward to it. > > -- > Dave Abrahams > Boost Consulting > www.boost-consulting.com Cheers, Gottfried

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RE: [C++-sig] Converting CString to/from std::string
by Kirsebom Nikolai Sept. 25, 2003

Sept. 25, 2003

-----Original Message----- From: Ralf W. Grosse-Kunstleve [mailto:rwgk@yahoo.com] Sent: 27. mai 2003 08:46 To: c++-sig(a)python.org Subject: Re: ÆC++-sigÅ Converting CString to/from std::string --- Nikolai Kirsebom <nikolai(a)micon.no> wrote: > I have a rather large set of C++ classes I want to make accessible > (initially only parts of some of the classes) from Python. I cannot > change the classes as they are defined and used throughout a large > application. Some of the methods take CString as parameters and others > return CString values. > > Does anyone have suggestion on how I can convert these parameters so > that I can use Boost.Python to generate the wrapper code. What do you want your CStrings to be in Python? Regular Python strings? If you think "yes" remind yourself that Python strings are immutable. I.e. if you have function signatures involving non-const references or pointers to CString as arguments or return values the mapping from C++ CStrings to Python strings will not work very well. More depending on your response. Ralf Some time ago I made a 'socket based' system (using BISON/FLEX for parsing) where I expose C++ objects to python. In this system CStrings are regular Python strings. So as an example I can write: --------------------------------------------- C++: class IF { CString MenuText; CString GetHelpText(); int SetHelpText(CString s); }; In Python: o = IF() # Behind the 'curtains' create a 'link' to a C++ object print o.MenuText s = o.GetHelpText(o.MenuText + "some text") ---------------------------------------------- So I would like something similar. I'm very new to the Boost system and do not really have experience in C++ Template development so I find the Reference Manual somewhat difficult to understand. This may explain if I request 'dead easy' or 'impossible' things. Thanks for any help Nikolai

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Re: pure virtual methods with pyste
by wiedeman＠gmx.net Aug. 26, 2003

Aug. 26, 2003

Hi Nicodemus, >Yes, it follows the procedure in the tutorial about abstract virtual >functions, ie, it only generates the virtual wrapper. You should still >be able to override the abstract member functions in Python, though... >is this the problem you're having? No, that's not my problem. I want to be able to use pointers to abstract classes within python without wrapping all the derived classes (in fact, they are plugins), and, if possible, without writing a call_f function for every pure virtual method. I've played around with boost.python and found the solution below (Test.cpp). With pyste, i'd get an empty class Abstract. I wonder, if my solution is dangerous or even wrong ? Thanks in advance, Christoph /* Test.cpp */ struct Abstract { virtual void a() = 0; }; #include <boost/python.hpp> using namespace boost::python; BOOST_PYTHON_MODULE(myclasses) { class_<Abstract, AbstractWrap, boost::noncopyable>("Abstract") .def("a", &Abstract::a) ; }

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RE: [C++-sig] Patches for pyste regarding exception specification s
by Gottfried.Ganssauge＠HAUFE.DE Aug. 16, 2003

Aug. 16, 2003

... > Thanks a lot Gottfried, your patch looks very clean! I will > commit it as > soon as Prabhu and I have fixed the "Order Bug". Good luck! > > Just one thing I didn't understand, could you explain this change? > > - def SetCurrent(self, current): > + def SetCurrent(self, current, missing = None): > + if missing is not None: > + pass > + This is one of the "fixes" I mentioned in my post. Originally I planned to print a message or throw an exception when missing wouldn't be None because I didn't know what to make of that parameter. Without it I got a 'wrong number of parameters' exception but I somehow got distracted and forgot about it when I came back and didn't get any more of those exceptions. I guess that this parameter should really be called "unused" because it needs to be there only for compatibility to MultipleCodeUnit.SetCurrent(), right? > > Thanks again! my pleasure > Nicodemus. Cheers, Gottfried

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def_readonly and const array members
by Jeff Brewer Aug. 6, 2003

Aug. 6, 2003

I am trying to wrap structs that have character arrays and I'm having problems since I moved from MSVC 7 to MSVC 7.1 (VS .NET 2003). Here is the struct I'm trying to expose the theArray member of using class_::def_readonly: struct testStruct { unsigned char theArray[16]; }; I've created a to_python converter for the unsigned char [16] type but I'm getting a "TypeError: No to_python (by-value) converter found for C++ type: unsigned char const volatile [8]" when I try to access the theArray member in Python. I've tried putting volatile in my typedef for the array, but that doesn't seem to help (how C++ binds these type modifiers always confuses me so maybe I put it in the wrong place). Thank you for the help, Jeff Brewer jeff(a)purplemagma.com p.s. The full code follows: Python code: import test theStruct = test.getStruct() print theStruct.theArray C++ code: typedef unsigned char uchar16array[16]; struct uchar16array_to_python { static PyObject *convert(uchar16array const &value) { PyObject *result = PyTuple_New(16); for (int i = 0; i < 16; i++) PyTuple_SetItem(result,i,PyInt_FromLong(value[i])); return result; } }; struct testStruct { unsigned char theArray[16]; }; testStruct getStruct() { static testStruct theStruct = {{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16}}; return theStruct; } BOOST_PYTHON_MODULE(test) { to_python_converter<uchar16array, uchar16array_to_python>(); class_<testStruct>("testStruct", init<>()) .def_readonly("theArray", &testStruct::theArray); def("getStruct", getStruct); }

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args patch
by Nikolay Mladenov Aug. 4, 2003

Aug. 4, 2003

Dave, I am posting the diffs from 1.29.0 plus the test and doc files. Sorry for the delay. I hope you won't have problems applying the diffs. Nikolay 44a45,52 > keywords<size+1> operator , (const keywords<1> &k) const > { > python::detail::keywords<size+1> res; > std::copy(elements, elements+size, res.elements); > res.elements[size] = k.elements[0]; > return res; > } > keywords<size+1> operator , (const char *name) const; 46a55,57 > > > 97a109,129 > struct arg : detail::keywords<1> > { > template <class T> > arg &operator = (T const &value) > { > elements[0].default_value = handle<>(python::borrowed(object(value).ptr())); > return *this; > } > explicit arg (char const *name){elements[0].name = name;} > operator detail::keyword const &()const {return elements[0];} > }; > > namespace detail > { > template <std::size_t nkeywords> > inline keywords< keywords<nkeywords>::size+1 > keywords<nkeywords>::operator , (const char *name) const > { > return this->operator , (arg(name)); > } > } > 21a22 > keyword(char const* n=0):name(n){} 57a58 > unsigned m_nkeyword_values; 35a36 > , m_nkeyword_values(0) 42d42 < 48a49,52 > object tpl (handle<>( > PyTuple_New(names_and_defaults[i].default_value ? 2 : 1) > )); > 50,51c54,55 < m_arg_names.ptr() < , i + keyword_offset --- > tpl.ptr() > , 0 55a60,77 > > if(names_and_defaults[i].default_value) > { > PyTuple_SET_ITEM( > tpl.ptr() > , 1 > , incref(names_and_defaults[i].default_value.get()) > ); > > ++m_nkeyword_values; > } > > > PyTuple_SET_ITEM( > m_arg_names.ptr() > , i + keyword_offset > , incref(tpl.ptr()) > ); 82c104 < if (total_args >= f->m_min_arity && total_args <= f->m_max_arity) --- > if (total_args + f->m_nkeyword_values >= f->m_min_arity && total_args <= f->m_max_arity) 85c107 < if (nkeywords > 0) --- > if (nkeywords > 0 || total_args < f->m_min_arity) 94,95c116,117 < // build a new arg tuple < args2 = handle<>(PyTuple_New(total_args)); --- > // build a new arg tuple, will adjust its size later > args2 = handle<>(PyTuple_New(f->m_max_arity)); 102c124,128 < for (std::size_t j = nargs; j < total_args; ++j) --- > std::size_t j = nargs; > std::size_t k = nargs; > std::size_t size = PyTuple_GET_SIZE(f->m_arg_names.ptr()); > > for (; j < f->m_max_arity && j < size ; ++j) 104,105c130,138 < PyObject* value = PyDict_GetItem( < keywords, PyTuple_GET_ITEM(f->m_arg_names.ptr(), j)); --- > PyObject* kwd = PyTuple_GET_ITEM(f->m_arg_names.ptr(), j); > > PyObject* value = nkeywords ? PyDict_GetItem( > keywords, PyTuple_GET_ITEM(kwd, 0)) : 0; > > if (!value) > { > if (PyTuple_GET_SIZE(kwd) > 1) > value = PyTuple_GET_ITEM(kwd, 1); 113c146,170 < PyTuple_SET_ITEM(args2.get(), j, incref(value)); --- > }else > ++k; > > PyTuple_SET_ITEM(args2.get(), j, incref(value) > ); > } > > if (args2.get()) > { > //check if we proccessed all the arguments > if(k < total_args) > args2 = handle<>(); > > //adjust the parameter tuple size > if(j<f->m_max_arity) > { > handle<> args3( PyTuple_New(j) ); > > for (size_t l = 0; l != j; ++ l) > { > PyTuple_SET_ITEM(args3.get(), l, PyTuple_GET_ITEM(args3.get(), l) ); > PyTuple_SET_ITEM(args2.get(), l, 0); > } > args2 = args3; > } ''' >>> from keywords import * >>> f = Foo() >>> f.a(), f.b(), f.n() (0, 0.0, '') >>> f = Foo(1) >>> f.a(), f.b(), f.n() (1, 0.0, '') >>> f = Foo(1,1.0) >>> f.a(), f.b(), f.n() (1, 1.0, '') >>> f = Foo(1,1.0,"1") >>> f.a(), f.b(), f.n() (1, 1.0, '1') >>> f = Foo(a=1) >>> f.a(), f.b(), f.n() (1, 0.0, '') >>> f = Foo(b=1) >>> f.a(), f.b(), f.n() (0, 1.0, '') >>> f = Foo(n="1") >>> f.a(), f.b(), f.n() (0, 0.0, '1') >>> f = Foo(1,n="1") >>> f.a(), f.b(), f.n() (1, 0.0, '1') >>> f.set() >>> f.a(), f.b(), f.n() (0, 0.0, '') >>> f.set(1) >>> f.a(), f.b(), f.n() (1, 0.0, '') >>> f.set(1,1.0) >>> f.a(), f.b(), f.n() (1, 1.0, '') >>> f.set(1,1.0,"1") >>> f.a(), f.b(), f.n() (1, 1.0, '1') >>> f.set(a=1) >>> f.a(), f.b(), f.n() (1, 0.0, '') >>> f.set(b=1) >>> f.a(), f.b(), f.n() (0, 1.0, '') >>> f.set(n="1") >>> f.a(), f.b(), f.n() (0, 0.0, '1') >>> f.set(1,n="1") >>> f.a(), f.b(), f.n() (1, 0.0, '1') ''' def run(args = None): import sys import doctest if args is not None: sys.argv = args return doctest.testmod(sys.modules.get(__name__)) if __name__ == '__main__': print "running..." import sys sys.exit(run()[0])

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cvs anonymous user access denied
by Roman Yakovenko Aug. 4, 2003

Aug. 4, 2003

Hi. Is there is easy way to get all current files from cvs ? Thanks

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First pass at exception translator template
by Gavin Doughtie July 31, 2003

July 31, 2003

So, this is probably gross or non thread-safe in some manner that I'm not clued into yet. I'd appreciate any elegant refactorings, but this seems to work and will allow me to just specify a bunch of "REGISTER_EXCEPTION" lines in my module. --------8<------------------------------- template <typename ExceptionType> struct ExceptionTranslator { typedef ExceptionTranslator<ExceptionType> type; static PyObject *pyException; static void RegisterExceptionTranslator(scope & scope, const char* moduleName, const char* name) { // Add the exception to the module scope std::strstream exName; exName << moduleName << "." << name << '\0'; pyException = PyErr_NewException(exName.str(), NULL, NULL); handle<> instanceException(pyException); scope.attr(name) = object(instanceException); // Register a translator for the type register_exception_translator< ExceptionType > ( &ExceptionTranslator<ExceptionType>::translateException ); } static void translateException(const ExceptionType& ex) { PyErr_SetString(pyException, ex.getMessage().ptr()); } }; template<typename ExceptionType> PyObject* ExceptionTranslator<ExceptionType>::pyException; // Convenience macro #define REGISTER_EXCEPTION(scopeRef, moduleName, className) \ ExceptionTranslator<className>::RegisterExceptionTranslator(scopeRef, moduleName, #className) // Module ====================================================================== BOOST_PYTHON_MODULE(my_module) { scope moduleScope; REGISTER_EXCEPTION(moduleScope, "my_module", InstanceException); ..... } -- Gavin Doughtie DreamWorks SKG

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Re: C++-sig digest, Vol 1 #658 - 7 msgs
by Jonathan Brandmeyer July 31, 2003

July 31, 2003

----- Original Message ----- > To: c++-sig(a)python.org > From: David Abrahams <> > Date: Wed, 30 Jul 2003 19:49:07 -0400 > Subject: [C++-sig] Re: implititly_convertible<>() difficulty > Reply-To: c++-sig(a)python.org > > --=-=-= > For recent GCCs, that should now be fixed in CVS. The enclosed patch > should also address the problem > > snipped patch to boost/python/object_operators.hpp As far as recent GCC's go, I tested this with GCC 3.3.1 (Debian prerelease dated last week) and it failed there too. My other environment is on Debian Sid with GCC 3.3.1, GCC 3.2.3 (tested using both) Boost.Python 1.30.0-4 (includes debian patches for gcc 3.3) and Python 2.2.3. The patch depends on some stuff in boost/iterator/ that is not present in Boost 1.30.0, so it did not work for me. Even if it did, the example I posted is only one of the areas that this fails. I am attempting to apply this implicit conversion to several dozen functions, member functions, and setters (all for the same tuple-like type), so the method of manually providing overloads isn't really scalable. Nor is it obvious to me how that would work for setters. I apologize for the lag time. I'm not on daily digest anymore, so hopefully this discussion will proceed better. Thanks, Jonathan Brandmeyer

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Automatic PyUnicode to 'const char*'
by Lijun Qin July 31, 2003

July 31, 2003

Hi all, I'm using boost.python to wrap the WTL (Windows Template Libaray), using VC 7.1 and porting some old code previously use win32ui.pyd. Basically it is easy to do, though gccxml failed to parse the ATL/WTL code so I can not use Pyste. But there is a trouble, does anybody know how to automaticly convert PyUnicode to 'const char *'? Without this, I have to change lot of code lines to explictly use str() function. Lijun Qin http://www.solidshare.com

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