In <w_adny5q3jzyxjrxnz2dnuvz_u2dn...@pdx.net> Scott David Daniels
<scott.dani...@acm.org> writes:
>kj wrote:
>> ... I can't come with an example in which the same couldn't be
>> accomplished with
>>
>> try:
>> # do something
>> # do something else
>> except ...:
>> # handle exception
>>
>> The only significant difference I can come up with is that in the
>> second form, the except clause may be masking some unexpected
>> exceptions from the "do something else" part. Is this the rationale
>> behind this else clause? Or is there something more to it?
>Yes, in a way. The idea of catching particular exceptions is to only
>handle exceptions you expect (let the others go out to more general
>reporters). So, not only should you choose the tightest exception to
>catch that you can, but you should look for it in a very narrow window:
>exactly where you expect it.
> try:
> v = mumble.field
> except AttributeError:
> pass
> else:
> sys.warning('field was actually there?')
>as opposed to:
> try:
> v = mumble.field
> sys.warning('field was actually there?')
> except AttributeError:
> pass
>The idea is to make it clear what you expect might go
>wrong that you are prepared to handle.
Wow. As rationales for syntax constructs go, this has got to be
the most subtle one I've ever seen...
Thanks!
kynn
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