Funny thing, it seems like you don't get it in the same way I did not
in the first place. His example is more like:
try:
try:
raise IndexError()
except:
raise CustomError() from __NoContext__
except CustomError as e:
# nevermind, let's see the whole thing after all
raise e from __OupsLooksLikeINeedContextAfterAll__
On 2012-02-03, at 12:29 PM, Barry Warsaw wrote:
> On Feb 03, 2012, at 08:52 AM, Ethan Furman wrote:
>
>> Not sure I'll ever use it this way, but:
>>
>> try:
>> try:
>> raise IndexError()
>> except:
>> raise CustomError() from None
>> except CustomError as e:
>> # nevermind, let's see the whole thing after all
>> raise e from Ellipsis
>
> In that context, I have to say that the last line, even if it were written
>
> raise e from ...
>
> is certainly cute, but not very informative. Triple-dots will be confusing
> and difficult to read in documentation and code, and Ellipsis has no logical
> connection to the purpose of this PEP. So while I'm +1 on everything else in
> the PEP, I'm -1 on this particular decision.
>
> One of the alternatives states:
>
> Create a special exception class, __NoException__.
>
> Rejected as possibly confusing, possibly being mistakenly raised by users,
> and not being a truly unique value as None, True, and False are.
>
> I think this should be revisited. First, `__NoException__` doesn't need to be
> an exception class. Ellipsis isn't so this doesn't need to be either. I have
> no problem adding a new non-exception derived singleton to mark this. And
> while __NoException__ may be a little confusing, something like __NoCause__
> reads great and can't be mistaken for a raiseable exception.
>
> So your example would then be:
>
> try:
> try:
> raise IndexError()
> except:
> raise CustomError() from None
> except CustomError as e:
> # nevermind, let's see the whole thing after all
> raise e from __NoCause__
>
> Cheers,
> -Barry
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