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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