Re: [Python-Dev] Idea for avoiding exception masking

29 Jan 2003

      Barry A. Warsaw wrote:
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"KY" == Ka-Ping Yee  writes:
>> Python code has a number of cases where a higher level routine
    >> traps an exception and reraises it with new information and
    >> losing the lower level error detail in the process.
KY> How about just holding on to the original exception and
    KY> storing it as an attribute (e.g. "cause") on the new
    KY> exception?
+1.  You may actually have a chain of exceptions so being able to
follow these using a well-known attribute is a good thing.
It would be good to not only hold on to the exception, but to
be able to tell where the original exception originated, i.e. to
be able get a traceback for both exceptions.

See
http://mail.python.org/pipermail/python-dev/2002-March/021846.html
for an old thread about this topic.

So what would exception chaining mean for the C API?

PyErr_SetString(PyExc_TypeError, "wrong type");
PyErr_SetString(PyExc_TypeError, "can't iterate");

The second call would normalize the first exception and attach
it to the second as the cause attribute? But then the second
exception would have to be normalized too.

Bye,
    Walter Dörwald