Mypy is still in development. Most Python features are supported.
Dropbox releases PyAnnotate
15 November 2017: Dropbox has released an open source tool for automatically generating type annotations based on runtime type collection. See the blog post for details. -Guido van Rossum
For more mypy news see the mypy blog
24 October 2017: We're increasing mypy's release frequency to about once per three weeks. We no longer will link here to each separate release blog post; just check the mypy blog for news. Two new versions, 0.530 and 0.540, were released since the last news item below. -Guido van Rossum
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
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.