Python has optional typing support in the standard library since version 3.5. Granted, not type _checking_, but that is offloaded to external tools like mypy[0]

Python has optional typing support in the standard library since version 3.5. Granted, not type _checking_, but that is offloaded to external tools like mypy[0]. I feel that gradual typing offers the best of both worlds: rapid prototyping, but also the strictness of types where you need it. 0: http://mypy-lang.org/ http://mypy-lang.org/