On 05/21/2013 04:23 AM, Nick Coghlan wrote:
On Tue, May 21, 2013 at 5:17 PM, Hrvoje Niksic <hrvoje.nik...@avl.com> wrote:
On 05/20/2013 05:15 PM, Ethan Furman wrote:
1) Do nothing and be happy I use 'raise ... from None' in my own
libraries
2) Change the wording of 'During handling of the above exception, another
exception occurred' (no ideas as to what at
the moment)
The word "occurred" misleads one to think that, during handling of the real
exception, an unrelated and unintended exception occurred. This is not the
case when the "raise" keyword is used. In that case, the exception was
intentionally *converted* from one type to another. For the "raise" case a
wording like the following might work better:
The above exception was converted to the following exception:
...
That makes it clear that the conversion was explicit and (hopefully)
intentional, and that the latter exception supersedes the former.
This ship sailed long ago (it was covered by the original exception
chaining spec in PEP 3134). If you want to deliberately replace an
exception while retaining the full traceback, you use "raise X from
Y", and the intro text will change to something like "This exception
was the direct cause of the following exception:"
I had forgotten about that, Nick, thanks.
So the moral of the story for our library code and replacing exceptions is we
should either do
raise ... from OldException
or
raise ... from None
depending on the importance of the originating exception.
And, of course, we only make these changes when we're already modifying the
module for some other reason.
--
~Ethan~
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