> Most “scripting” languages don't support annotations for checking parameters and return values

PEP 3107 introduced function annotations to Python 3. The following syntax is valid:

    >>> def square(n: int) -> int:
    ...     return n * n
    ...
    >>> square(3)
    9

Nothing is done with annotations by default. Here's an article discussing this "unused feature": http://ceronman.com/2013/03/12/a-powerful-unused-feature-of-...