On Wed, Jun 24, 2020 at 7:27 AM M.-A. Lemburg <mal@egenix.com> wrote:
Wow, so 19 years after PEP 275, we are indeed getting a switch statement. Nice :-)
Indeed. Fortunately there are now some better ideas to steal from other languages than C's switch. :-) Something which struck me as odd when first scanning through the PEP
is the default case compared to other Python block statements:
match something: case 0 | 1 | 2: print("Small number") case [] | [_]: print("A short sequence") case str() | bytes(): print("Something string-like") case _: print("Something else")
rather than what a Pythonista would probably expect:
match something: case 0 | 1 | 2: print("Small number") case [] | [_]: print("A short sequence") case str() | bytes(): print("Something string-like") else: print("Something else")
Was there a reason for using a special value "_" as match-all value ? I couldn't find any explanation for this in the PEP.
Nearly every other language whose pattern matching syntax we've examined uses _ as the wildcard. The authors don't feel very strongly about whether to use `else:` or `case _:`. The latter would be possible even if we added an explicit `else` clause, and we like TOOWTDI. But it's clear that a lot of people *expect* to see `else`, and maybe seeing `case _:` is not the best introduction to wildcards for people who haven't seen a match statement before. A wrinkle with `else` is that some of the authors would prefer to see it aligned with `match` rather than with the list of cases, but for others it feels like a degenerate case and should be aligned with those. (I'm in the latter camp.) There still is a lively internal discussion going on, and we'll get back here when we have a shared opinion. -- --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-c...>