Thanks for the reply. Independent of whether the spelling is encouraged, does the PEP in its current form consider `(name := _)` to be legal, or is `_` forbidden on the RHS of a `:=` by a similar argument to forbidding `_` in `**_`?
Eric On Wed, 24 Jun 2020 at 16:12, Guido van Rossum <gu...@python.org> wrote: > On Wed, Jun 24, 2020 at 5:23 AM Eric Wieser <wieser.eric+nu...@gmail.com> > wrote: > >> In regards to >> https://www.python.org/dev/peps/pep-0622/#alternatives-for-constant-value-pattern, >> was this alternative considered? >> ``` >> match obj: >> case SomeClass(field := _): # is this already allowed by the PEP? >> pass >> case some_constant: # my proposal: do not require `.some_constant` >> here >> pass >> case (other := _): # is this already allowed by the PEP? If so, do >> we need the extra `case other:` spelling? >> print(other) >> ``` >> >> It seems like `:=` already provides all the necessary syntax for >> distinguishing bindings from constants, admittedly at the cost of 6 >> characters per binding (eg `Point(x := _, y := _)`) - so introducing >> additional syntax seems unnecessary. >> > > In languages that have pattern matching, it is the primary way to extract > pieces of a compound data structure into individual variables. For the use > cases where match would be a good fit in Python, the same will be true. So > using your proposed syntax here is too verbose to consider. > > >> If this was considered but rejected for verbosity concerns, it would be >> nice to see it mentioned in the rejected alternatives section. >> > > We can't discuss every single idea in that section. I don't think anyone > else has proposed this, so I don't think it needs to be discussed for > posterity. There are plenty of better ideas in this thread that deserve a > mention there. > > -- > --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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