On Fri, Feb 7, 2020 at 7:56 AM Ethan Furman <et...@stoneleaf.us> wrote:
> On 02/07/2020 07:33 AM, Serhiy Storchaka wrote:
> > 07.02.20 16:28, Ram Rachum пише:
> >> The idea is to add `raise as` syntax, that raises an exception while
> setting the currently caught exception to be the cause. It'll look like
> this:
> >>
> >> try:
> >> 1/0
> >> except ZeroDivisionError:
> >> raise as ValueError('Whatever')
> >>
> >> What it does is a shorter version of this:
> >>
> >> try:
> >> 1/0
> >> except ZeroDivisionError as error:
> >> raise ValueError('Whatever') from error
> >
> > How does it differ from
> >
> > try:
> > 1/0
> > except ZeroDivisionError:
> > raise ValueError('Whatever')
>
> Here's a diff:
>
> $ diff no_from.py with_from.py
> 3,4c3,4
> - ... except ZeroDivisionError:
> - ... raise ValueError('Whatever')
> ---
> + ... except ZeroDivisionError as e:
> + ... raise ValueError('Whatever') from e
> 10c10
> - During handling of the above exception, another exception occurred:
> ---
> + The above exception was the direct cause of the following exception:
>
>
> To me the difference between "raise from" and "raise" is the implicit
> meaning:
>
> - "During handling of ..." implies that the second exception should not
> have occurred and there is a bug in the exception handling code
>
> - "The above exception ..." implies that this code path is normal and
> extra information is being supplied
>
They also set different attributes on the exception to communicate the
trigger of the exception, so there's also a structural difference beyond
just the textual one.
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