On Fri, Jan 30, 2015 at 8:56 AM, Marko Rauhamaa <ma...@pacujo.net> wrote:
> Ian Kelly <ian.g.ke...@gmail.com>:
>
>> Like I suggested earlier, just don't catch the inner exception at all.
>> The result will be both exceptions propagated, chained in the proper
>> order.
>
> Depends on the situation.
Like what? If you want to specifically propagate the original
exception in order to be caught again elsewhere, then I think there's
a code smell to that. If this inner exception handler doesn't
specifically know how to handle a ValueError, then why should some
outer exception handler be able to handle an exception that could have
come from virtually anywhere?
A better approach to that would be to create a specific exception
class that narrowly identifies what went wrong, and raise *that* with
the other exceptions chained to it. E.g.:
try:
do_interesting_stuff()
except ValueError as e:
try:
log_it()
except Exception:
# Chain both exceptions as __context__
raise SpecificException
else:
# Chain the original exception as __cause__
raise SpecificException from e
Or if you don't care about distinguishing __cause__ from __context__:
try:
do_interesting_stuff()
except ValueError:
try:
log_it()
finally:
raise SpecificException
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