Guido van Rossum, best known as designer of the Python programming language, recently sent out a proposal on the python-ideas mailing list for adding type annotations to Python function declarations.

This is clearly not what you wanted to do. Python versions 3.6 and higher provide “type annotations,” a feature that enables you to define the type of data each function argument should take.

Notice that Python introduced a new syntax (the -> arrow), and allowed me to stick an annotation before the end-of-line colon, in order for annotations to work.

This is clearly not what you wanted to do. Python versions 3.6 and higher provide “type annotations,” a feature that enables you to define the type of data each function argument should take.

Mypy, Pytype, Pyright, and Pyre can help you keep your type-hinted Python code bug-free. Let’s see what each of these useful tools has to offer.