Re: [C++-sig] export custom C++ exception to Python so it can beraisedby python
Hi Giuseppe,
thank you for the detailed response!
On 11/07/2012 08:56 AM, Giuseppe Corbelli wrote:
On 06/11/2012 15:35, Martin Hellmich wrote:
I've based my code on.
http://stackoverflow.c om/questions/9620268/boost-python-custom-exception-class
I have used the same reference and also this suggestion for including the
other attributes shown here:
http://stackoverflow.com/questions/11448735/boostpython-export-custom-exception-and-inherit-from-pythons-exception
However, this doesn't solve my problem.
It works fine when I throw the MyException in C++, but when I raise the
MyCPPException in Python, the translator is not called (which makes
sense), so
the attribute 'cause' does not change.
Actually, before I throw the MyException for the first time in C++,
MyCPPException does not have the attribute 'cause' at all.
Of course.
This issue should be the same, if I set the exception with
PyErr_SetObject,
since the translator is not called, when I 'raise' it.
Very likely the SetString uses SetObject under the hood, but I never
used SetObject.
I'd try to:
*) As you were writing before, declare a C++ class MyException: public
std::exception {
MyException();
MyException(int code, const std::string &string);
int code();
const char* what();
int errorCode;
std::string errorMessage;
};
*) Wrap it as a bpy::class_ so you can use it like a standard exception
with all the attributes you need.
This is the part that I miss, I guess. How can I wrap a class so that it
works like an exception in python? In the solutions on stackoverflow the
translation to an exception only happens in the translator, meaning that
I cannot call 'raise MyException' in python, as it doesn't inherit from
(the python) Exception.
PyErr_NewException has to be based on a type of python Exception, so I
cannot base it on my c++ class, right?
Have you ever used the 3rd parameter to specify a dict?
Cheers
Martin
*) Register an exception translator as defined before. Maybe the
to-python conversion performed in the exception translator does work
even if you have wrapped MyException as a standard class.
--
Martin HellmichInformation Technology Department
mhell...@cern.chCERN
+41 22 76 765 26 CH-1211 Geneva 23
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Re: [C++-sig] export custom C++ exception to Python so it can beraisedbypython
On 07/11/2012 09:24, Martin Hellmich wrote:
*) As you were writing before, declare a C++ class MyException: public
std::exception {
MyException();
MyException(int code, const std::string &string);
int code();
const char* what();
int errorCode;
std::string errorMessage;
};
*) Wrap it as a bpy::class_ so you can use it like a standard exception
with all the attributes you need.
This is the part that I miss, I guess. How can I wrap a class so that it works
like an exception in python? In the solutions on stackoverflow the translation
to an exception only happens in the translator, meaning that I cannot call
'raise MyException' in python, as it doesn't inherit from (the python)
Exception.
I've had a closer look. What if we take WindowsError as an example?
*) Define a new python exception CustomError with python/C APIs based on
WindowsError
*) Define a new C++ exception CustomException based on std::exception
*) Register a translator from C++ to python using CustomError as a target
Seems a reasonable approach.
--
Giuseppe Corbelli
WASP Software Engineer, Copan Italia S.p.A
Phone: +390303666318 Fax: +390302659932
E-mail: giuseppe.corbe...@copanitalia.com
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Re: [C++-sig] buildin converter for long double
Dear Jiang, thanks I got it to work by using my own version of `builtin_converters.hpp` locally together with the code that you recommended. -Holger On Tue, Nov 6, 2012 at 3:25 AM, jiangzuo...@gmail.com wrote: > how about return a wrap type of long double to cheating boost/python, and > register youself converter as > > PyObject * o = PyArrayScalar_New(LongDouble); > PyLongDoubleScalarObject * s = (PyLongDoubleScalarObject*)o; > s->obval = value; > > Don't forget to call import_array() in your model init function. > > BTW, I think float128 is not useful, it's slow. and in most case, change > algorithm to avoid precision problem is another *better* approach. > > > Changsheng Jiang > > > On Mon, Nov 5, 2012 at 6:27 PM, Holger Brandsmeier > wrote: >> >> Dear list, >> >> the boost python buildin converter for long double: >> BOOST_PYTHON_TO_PYTHON_BY_VALUE(long double, >> ::PyFloat_FromDouble(x), &PyFloat_Type) >> converter/builtin_converters.hpp >> identifies long double, which on my system is a 128bit float, with a >> 64bit float in python. I would like to identify it with numpy`s >> float128. Can you give me any hings how I would be able to do that? >> >> -Holger >> ___ >> Cplusplus-sig mailing list >> Cplusplus-sig@python.org >> http://mail.python.org/mailman/listinfo/cplusplus-sig > > > > ___ > Cplusplus-sig mailing list > Cplusplus-sig@python.org > http://mail.python.org/mailman/listinfo/cplusplus-sig ___ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
