Linters are indeed excellent tools. A "what's wrong" which the linters don't find is that for/else is one of the more confusing aspects of the Python language,

Linters are indeed excellent tools. A "what's wrong" which the linters don't find is that for/else is one of the more confusing aspects of the Python language, and should be avoided when there are equally clear alternatives. That is, I believe that for entry in entries: if entry == key: break else: raise NotFoundError is better written as: if not any(entry == key for entry in entries): raise NotFoundError