"I can't think of any code I've personally written in, say, the past five years which used tests or runtime type checks to try to catch type-related bugs. In fa

"I can't think of any code I've personally written in, say, the past five years which used tests or runtime type checks to try to catch type-related bugs. In fact over the past ten years I can only think of one time when a static type checker would've caught a bug that got as far as being committed." This is clearly a case of "you don't know what you don't know." I strongly suspect that there are many things you deem "not something static typing would catch" that I have been catching with static typing. From the trivial (passing bid price where ask is expected) to the simple (keeping track of which array this index is supposed to point into) to the tricky (restricting certain behaviors to certain threads). And those three examples were from my last big C project - no esoteric type system (some of which make it even more powerful and even more convenient). I won't go so far as to argue that extensive use of static checking is always a win, but it is a tool I find very effective. And it looks very little like "assert isinstance" strung about a Python codebase.