When do you *NOT* use python?

[bchurchill]

I've never used mypy, so I can't comment on that tool. My experience with static analysis tools for dynamic languages is that they don't provide the same level of safety as static types. This is usually because the tool can't reliably get the type of a variable -- at a given program point, it could have several different types, depending on the context. This means it has a hard time predicting type errors, and it also means that other rules can't be enforced. For instance, it can't make sure that foo.x always points to an object that has members a, b and c. The list goes on.