Thanks for the feedback everyone. I've only encountered the use case once,
like you've mentioned it's probably not worth the effort given that it's
such a small problem space.
Thanks again!
On Tue, Jan 4, 2022, 00:18 Steven D'Aprano <st...@pearwood.info> wrote:
> On Mon, Jan 03, 2022 at 11:31:30PM -0500, elvis kahoro wrote:
>
> > I was hoping there could be some syntax to extend pattern matching to
> > handle exceptions such that we could handle patterns with multiple types
> of
> > exceptions like so:
> >
> > match *this_raises_an_exception*, *this_raises_another_exception*:
> > case *AttributeError*, *TypeError*:
> > print("catches attribute and type errors")
> > case *AttributeError*, *AttributeError*:
> > print("catches attribute and attribute")
>
> Can you explain why you want to do that?
>
> Right now, to do something like that you would need something like this:
>
> err1 = err2 = None
> try:
> x = this_raises_an_exception
> except AttributeError as e:
> err1 = e
> try:
> y = this_raises_another_exception
> except (AttributeError, TypeError) as e:
> err2 = e
>
> if err1 is err2 is None:
> # handle the case where neither expression raised
> print(x, y)
>
> elif err1 is None or err2 is None:
> # only one expression raised
> print("everything else")
>
> elif isinstance(err1, AttributeError):
> if isinstance(err2, AttributeError):
> print("two Attribute Errors")
>
> elif isinstance(err2, TypeError):
> print("Attribute Error and Type Error")
>
> else:
> print("everything else")
>
> else:
> print("everything else")
>
>
> or something equally convoluted. I agree that if you are currently
> writing code this horrible, the idea of using a match statement would
> seem attractive.
>
> But... are you actually writing this sort of horrible, convoluted,
> complex, complicated mess of code? Why??? Please explain your actual
> concrete use-case for this. Otherwise it looks to me like an
> over-generalisation.
>
> I think I would need to see a sketch of *real* code to understand why
> you want this.
>
> As I see it, there are three realistic use-cases, all which can be
> handled with existing syntax:
>
> * protect the match expression in a try...except:
>
> try: x = expression
> except SomeError: ...
> match x: ...
>
> * protect a case block in a try...except:
>
> match expression:
> case something:
> try:
> block
> except SomeError: ...
>
>
> * protect the whole construct in a try...except:
>
> try:
> match expression:
> case something:
> block
> except:
> log(something)
> raise
>
>
> Anything else seems to me to be YAGNI; too complex and complicated to
> care about.
>
> Convince me that I'm wrong.
>
>
>
> --
> Steve
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