It's interesting that pattern matching has been accepted despite a poll showing a majority (65%) of core developers opposed to this particular proposal, and a plurality (44%) opposed to pattern matching altogether.
I'm not sure if you can read the 'accept 634 + another' options as opposed to 'accept 634' (that said you can't necessarily read it as in support of it either. This poll is a bit of a mess in that regard). But it's certainly contentious (all options including accepting 634 still only comes to 50%).
What matters (if the intent is to accurately determine the preferences of those voting) is whether those voting for those options would prefer rejecting all options or only accepting 634 (hence why ranked-choice voting is a thing). Either way it would probably be healthier for a larger consensus to form before committing to a decision.
Don't forget that the poll is dated 2020-11-20 (and majority of votes were cast soon). There was a lot of discussion (and thus maybe elaboration of opinions) since that.
Yes, the variable names in the case patterns are treated like variables on the left hand side of an assignment statement. Whatever value they may have had before is irrelevant. A pattern which consists solely of a variable name is a wildcard pattern that matches anything, just as it would be on the left side of an assignment.
Edit: It is possible to use constants or variables in a case pattern, but they have to be dotted names to not be treated like a capture pattern. So this would work for your example:
class HttpStatus(Enum):
NOT_FOUND = 404
match status:
case HttpStatus.NOT_FOUND:
return "Not found"
Couldn't we achieve the same functionality with a little less ambiguity using the following syntax?:
not_found = 404
match status:
case not_found:
return "Not found"
case _ as foo:
do_something(foo)
return "Match anything"
it even works for the example in PEP 365
match json_pet:
case {"type": "cat", "name": _ as name, "pattern": _ as pattern}:
return Cat(name, pattern)
case {"type": "dog", "name": _ as name, "breed": _ as breed}:
return Dog(name, breed)
case _:
raise ValueError("Not a suitable pet")
I'm with everyone on "incredibly disappointing" valuation. But being pragmatic, I had to accept the idea "it can be addressed later" vs continuing this mess. And there was truly mess, e.g. PEP642, which initially tried to addressed just this issue, turned in a hairy monster trying to random-patch pattern matching considerably in rather weird ways.
Accepted:
Specification https://www.python.org/dev/peps/pep-0634/
Motivation and Rationale https://www.python.org/dev/peps/pep-0635/
Tutorial https://www.python.org/dev/peps/pep-0636/
Rejected:
Unused variable syntax https://www.python.org/dev/peps/pep-0640/
Explicit Pattern Syntax for Structural Pattern Matching https://www.python.org/dev/peps/pep-0642/