try... except with unknown error types
tjreedy at udel.edu
Sun Aug 21 15:52:28 EDT 2011
On 8/21/2011 2:26 PM, Paul Rubin wrote:
> Steven D'Aprano<steve+comp.lang.python at pearwood.info> writes:
>>> But there's no way to know what that minimum is. Python libraries throw
>>> all sorts of exceptions that their documentation doesn't mention.
>> Yes, you're absolutely correct. But it's also irrelevant. Most of those
>> exceptions should not be caught, even if you know what they are, because
>> they represent either bugs that should be fixed, or bad data which should
>> raise an exception. A bare except, or except Exception, is hardly ever the
>> right approach.
> I'm not sure what to do instead. The exceptions I'm currently dealing
> with happen when certain network operations go wrong (e.g. network or
> remote host is down, connection fails, etc.) The remedy in each case is
> to catch the exception, log the error, and try the operation again
> later. But there's no guaranteed-to-be-complete list in the Python docs
> of all the exceptions that can be thrown. A new and surprising mode of
> network failure can lead to an unhandled exception, unless you catch
I would expect that catching socket.error (or even IOError) should catch
all of those.
A subclass of IOError, this exception is raised for socket-related
errors. It is recommended that you inspect its errno attribute to
discriminate between different kinds of errors."
> It's a retail application that would cause some business disruption and
> a pissed off customer if the program went down. Also it's in an
> embedded box on a customer site. It's not in Antarctica or anything
> like that, but it's a few towns over, and someone would have to drive
> there (probably through heavy traffic) if something went wrong that
> power cycling the box couldn't fix.
Terry Jan Reedy
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