Suggesting the use of StandardError as base of error Exceptions.

[Diez B. Roggisch]

Antoon Pardon schrieb:
> In a number of cases I have a program that looks like the following.
> 
> for case in all_cases:
>   try:
>     treat(case)
>   except Exception, ErrInfo:
>     generate_traceback()
> 
> The idea is to get as much information as possible when something
> goes wrong but at the same time treat as many cases as possible.
> 
> Then one day things broke. The reason was that in some circumstances
> treat would decide that things were beyond control and called sys.exit
> However sys.exit doesn't return to the O.S. immediately but raises
> SystemExit, which was caugth by the code and the loop continued.
> 
> I then took a look at http://docs.python.org/lib/module-exceptions.html
> which describes the exception heirarchy as follows:
> 
>     Exception
>      +-- SystemExit
>      +-- StopIteration
>      +-- StandardError
>      |   +
>      |   + All kind of error exceptions
>      |   + 
>      +---Warning
>          +
>          + All kind of warnings
>          +
> 
> and came to the conclusion, that it would be better to write my code
> as follows:
> 
> for case in all_cases:
>   try:
>     treat(case)
>   except StandardError, ErrInfo:
>     generate_traceback()
> 
> Unfortunatly this doesn't work either because a lot of the error
> exceptions in the stdlib (if not all) inherit directly from
> Exception instead of from StandardError. The documentation also
> seems to suggest this use for users exception.
> 
> Now I was wondering if it wouldn't be better that for exception
> that indicate some error condition that these would inherit
> from StandardError and that this would be indicated in the
> documentation and reflected in the stdlib?
> 
> Would it break much code to make this change? My first impression
> would be no, but I could be missing something.

There has been a discussion on this just a few days ago, have you read that? There is even a PEP mentioned.

http://groups.google.com/group/comp.lang.python/browse_thread/thread/56d7c5767a205866/d2403ae0c6267ca1


Diez