On Wed, Jun 24, 2020 at 3:02 AM Chris Jerdonek <chris.jerdo...@gmail.com> wrote:
> I have an exploratory question. In this section: > > The alternatives may bind variables, as long as each alternative binds the >> same set of variables (excluding _). For example: >> match something: >> ... >> case Foo(arg=x) | Bar(arg=x): # Valid, both arms bind 'x' >> ... >> ... > > > Tweaking the above example slightly, would there be a way to modify the > following so that, if the second alternative matched, then 'x' would have > the value, say, None assigned to it? > > match something: >> ... >> case Foo(arg=x) | Bar() (syntax assigning, say, None to x?) >> ... >> ... > > > That would let Bar be handled by the Foo case even if Bar doesn't take an > argument. I'm not sure if this would ever be needed, but it's something I > was wondering. I didn't see this covered but could have missed it. > That sounds like you are planning to put an 'if x is not None' check in the block. In most cases it would probably be cleaner to separate this out into two cases. (And yes, I can think of counterexamples, but they don't feel compelling enough to try and invent such syntax.) -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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