[PyQt] Raising C++ exceptions from python

[Phil Thompson]

On 13/10/2014 11:48 am, Alessandro Pasotti wrote:
> 2014-10-13 10:49 GMT+02:00 Phil Thompson <phil at riverbankcomputing.com>:
>> On 13/10/2014 8:48 am, Alessandro Pasotti wrote:
>>> 
>>> Hello,
>>> 
>>> What is the recommended way to raise/throw a C++ exception from 
>>> python
>>> to be catched in C++ code?
>>> 
>>> For example, I have this SIP code:
>>> 
>>> class QgsMapServiceException
>>> {
>>> %TypeHeaderCode
>>> #include <qgsmapserviceexception.h>
>>> %End
>>>   public:
>>>     QgsMapServiceException( const QString& code, const QString& 
>>> message );
>>>     QString code() const;
>>>     QString message() const;
>>> };
>>> 
>>> 
>>> In python code I would like to raise this exception and catch it from
>>> C++ FCGI loop.
>>> 
>>> The problem is that Python doesn't know that QgsMapServiceException 
>>> is
>>> an exception:
>>> 
>>>     raise QgsMapServiceException('ExceptionFilter', 'Test exception
>>> raised from ExceptionFilter')
>>> TypeError: exceptions must be old-style classes or derived from
>>> BaseException, not QgsMapServiceException
>> 
>> 
>> http://pyqt.sourceforge.net/Docs/sip4/directives.html#directive-%Exception
>> 
>> Phil
> 
> Hi Phil,
> 
> Thanks for pointing me to the right docs, I've now this SIP code but I
> cannot catch anything from C++ loop, it seems like the exceptions are
> silently ignored. I would like to raise exceptions from python and
> catch them in C++.
> 
> Any idea about where to look?
> Should I throw the exception from within RaiseCode ? (tried without 
> success).
> 
> 
> 
> %Exception QgsMapServiceException(SIP_Exception) 
> /PyName=QgsMapServiceException/
> {
> %TypeHeaderCode
> #include <qgsmapserviceexception.h>
> %End
> %RaiseCode
>   SIP_BLOCK_THREADS
>   PyErr_SetString(sipException_QgsMapServiceException,
> sipExceptionRef.message().toUtf8().constData() );
>   SIP_UNBLOCK_THREADS
> %End
> };

You might need...

http://pyqt.sourceforge.net/Docs/sip4/directives.html#directive-%VirtualErrorHandler

Phil