Python type hints are used ahead of time, by the type-checking system; for instance, in your editor or IDE. In other words, Python’s type hints are for the developer , not the runtime.

Defining a list in Python is easy—just use the bracket syntax to indicate items in a list, like this: list_of_ints = [1, 2, 3] Items in a list do not have to all be the same type; they can be ...

hello.py:7: error: Argument 1 to "hello" has incompatible type ↪"int"; expected "str" hello.py:8: error: Argument 1 to "hello" has incompatible type ↪"List[int]"; expected "str" Sure enough, mypy has ...