Mypy is still in development. Most Python features are supported.
Mypy 0.700 released
3 April 2019: Mypy 0.700 was released. It's up to 4x faster than previous releases! Read the blog post for more details. -Jukka Lehtosalo
Blog post on extending mypy with plugins
1 March 2019: Read a blog post about extending mypy with plugins and distributing the plugins together with PEP 561 packages. -Ivan Levkivskyi
Mypy 0.670 released
8 February 2019: Mypy 0.670 was released. Read the blog post for more details. -Guido van Rossum
Mypy 0.660 released
16 January 2019: Mypy 0.660 was released. Read the blog post for more details. -Michael J. Sullivan
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.