Custom C Exception Subclasses

Gabriel Genellina gagsl-py2 at
Wed Dec 24 18:24:59 CET 2008

En Wed, 24 Dec 2008 13:42:38 -0200, Ross <rlight2 at> escribió:

> For a project that I am doing, it would be useful to have an exception
> class that stores some additional data along with the message.
> However, I want to be able to store a couple pointers to C++ classes,
> so I can't just use an exception created with PyExc_NewException.

In fact you can, you could store those pointers as attributes of the  
exception object, using a PyCObject.
Accessing those attributes isn't as easy as doing exc->field, but I think  
it's easy enough. Inheriting from some exception type requires you to  
define the type structure and fill it right, and IMHO is a lot harder.

> If
> I were to subclass the built-in Exception type, I would need to have
> access to the PyExc_ExceptionObject, but the headers only give
> PyExc_Exception, the type object.  This seems like a rather
> straightforward task, but I can't seem to find any documentation for
> it.  Does anyone know how to do this?  Thanks!

Perhaps there is a misunderstanding here. To subclass a type, you need the  
type, not an instance of such type. The "Exception" class you use in  
Python code is "PyExc_Exception" in C code. Usually one would inherit a  
subclass, RuntimeError by example, so use PyExc_RuntimeError as the base  

Gabriel Genellina

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