On Tue, 05 Oct 2010 13:57:11 +1100, Ben Finney wrote:
> Here's your problem. Don't ever use a bare ‘except’ unless you know
> exactly why you're doing so. Rather, figure out what exception types you
> want to catch, and catch *only* those types.
If I use a bare except, I usually have a good reason, namely that the
documentation doesn't actually mention which exceptions can be raised.
This is usually because the code doesn't actually know which exceptions
can be raised.
If a module defines:
def foo(f):
f.bar()
...
the set of exceptions which foo() can raise is limitless. The user can
pass whatever they like as "f", and its bar() method can raise anything.
Knowing which exceptions a function or method can raise is the exception
rather than the rule.
If I'm catching exceptions in order to perform clean-up, I'll use a bare
except and re-raise the exception afterwards. In that situation, a bare
except is usually the right thing to do.
If I'm not going to re-raise the exception, I'll either catch Exception or
add explicit catches for SystemExit and KeyboardInterrupt which re-raise
the exception.
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