In Python even the trivial definition of "used" (i.e. "bound name which is referred to afterwards") is not that easy (e.g. getattr), linters go for the literal

In Python even the trivial definition of "used" (i.e. "bound name which is referred to afterwards") is not that easy (e.g. getattr), linters go for the literal definition instead ("bound name, which is statically referred to afterwards"). This works for 99 % of code. Your definition of "used" (~"influences the observable result") is of course fully within the dominion of Rice's theorem, though this particular example would be caught by any data-flow analyzer.