Larry Hastings wrote:
As for leveraging the convention of using '_' for values you don't care about in Python--that's actually why I /don't/ like it as the wildcard pattern. To date, everyone who uses '_' understands it's just an identifier, no different from any other identifier.
Not quite... I understand it more like a file in /tmp I don't use it for anything I will want later, just in case.
However, if I understand PEP 622 correctly, the places you use '_' as the wildcard pattern are also places where you could put an identifier. But in this one context, '_' doesn't behave like the other identifiers, even though in every other context in Python it still does. This is the "special case" that "breaks the rules" I alluded to above. Consistency with the longstanding semantics of '_', and consistency with other identifiers, is much more important to me than consistency with other languages for the pattern matching wildcard token.
If a normal variable name is re-used, I would expect it to have the same meaning. I know that "case x, x:" as shorthand for "case x, __x if x == __x:" has been postponed, but it could still happen later, and it would be a problem if that ever became legal without requiring the two bindings to match. I do NOT assume that they will match if the variable happens to be _, though I suppose others might. -jJ