[wting]

Using _ as a throwaway variable name is idiomatic in Python, Haskell, and Go. Looks like they're pushing the same idiom in Hack, which I'm ok with.

[agumonkey]

AFAIK in Haskell it's not a throwaway variable, a pattern with _ will not create a binding at all. I don't think Python does this, maybe Go.

[MBlume]

Python doesn't have language support for the idiom -- trying to evaluate

lambda _, _: None

gives

SyntaxError: duplicate argument '_' in function definition

but tools like pylint will silence unused-variable warnings if the variable starts with '_'.

[agumonkey]

Thanks for the verification. But even a bit of syntactic convention won't be enough if python create a unnecessary binding.

[wycats]

And Ruby, and Rust. It's close to universal.

[wtetzner]

And Clojure.