The existing type system (see e.g. http://mypy-lang.org/ http://mypy-lang.org/) is gradual. You can mix typed and untyped code, at the cost of some safety. You

The existing type system (see e.g. http://mypy-lang.org/ http://mypy-lang.org/) is gradual. You can mix typed and untyped code, at the cost of some safety. You can also write type stubs for libraries that don't provide type information.