Python is a dynamically typed language, and some of its appeal derives from this. Nevertheless, especially for large code bases, it would be nice if a compiler could find type errors before the code is even run. Optional static type checking promises exactly this, and over the past four years we have successfully introduced this feature into Python 3. This talk introduces the type system we've adopted and the syntax used for type annotations, some tips on how to get started with a large existing code base, and our experience using the 'mypy' type checker at Dropbox. The entire system is open source, and has also been adopted by other companies such as Lyft, Quora and Facebook.
Guido van Rossum is the creator of Python. Born in the Netherlands, he moved to the US following Python's success. He has worked at various startups and Google, and is currently a Principal Engineer at Dropbox.