Mypy is still in development. Most Python features are supported.
Mypy 0.521 released
25 July 2017: Mypy 0.521 was released. It is a minor bugfix release for 0.520, and everyone using 0.520 should upgrade. Read the blog post to see what's changed. -Jukka
Mypy 0.520 released
10 July 2017: Mypy 0.520 was released. It adds better control for Any types, __setattr__ support, more flexible NamedTuples, and many more improvements and bug fixes. Read the blog post to see what's changed. -Jukka
Mypy 0.510 released
5 May 2017: Mypy 0.510 was released. It adds support for overloads in source files and more flexible callables, but these are just a few of the improvements and fixes. Read the blog post to see what's changed. -Jukka
Mypy 0.501 released
1 Mar 2017: Mypy 0.501 was released. It switches to a new default parser and supports Python 3.6 features by default. These are also many other improvements and fixes. Read the blog post to see what's changed. -Jukka
def fib(n): a, b = 0, 1 while a < n: yield a a, b = b, a+b
def fib(n: int) -> Iterator[int]: a, b = 0, 1 while a < n: yield a a, b = b, a+b
Migrate existing code to static typing, a function at a time. You can freely mix static and dynamic typing within a program, within a module or within an expression. No need to give up dynamic typing — use static typing when it makes sense. Often just adding function signatures gives you statically typed code. Mypy can infer the types of other variables.
Mypy type checks programs that have type annotations conforming to PEP 484. Getting started is easy if you know Python. The aim is to support almost all Python language constructs in mypy.
Mypy has a powerful, modern type system with features such as bidirectional type inference, generics, callable types, abstract base classes, multiple inheritance and tuple types.
Many commonly used libraries have stubs (statically typed interface definitions) that allow mypy to check that your code uses the libraries correctly.