BerandaComputers and TechnologyMypy – Optional Static Typing for Python

Mypy – Optional Static Typing for Python

Why mypy?

Compile-time type checking
Static typing makes it easier to find bugs
with less debugging.
Easier maintenance
Type declarations act as
machine-checked documentation.
Static typing makes your code easier to understand and easier to modify
without introducing bugs.
Grow your programs from dynamic to static
typing
You can develop programs with dynamic typing and add
static typing after your code has matured, or migrate existing
Python code to static typing.

Mypy is an optional static type checker for Python that aims
to combine the benefits of dynamic (or “duck”) typing and static typing.
Mypy combines the expressive power and
convenience of Python with a powerful type system and compile-time type checking.
Mypy type checks standard Python programs; run them using any Python VM
with basically no runtime overhead.

Mypy 0.790 released

9 October 2020: Mypy 0.790 was released.
Read the
blog post
for the details.
-Jukka Lehtosalo

Mypy 0.780 released

3 June 2020: Mypy 0.780 was released.
Read the
blog post
for the details.
-Ivan Levkivskyi

Mypy 0.770 released

10 March 2020: Mypy 0.770 was released. This release includes various fixes and improvements and improved type inference in some cases.
Read the
blog post
for the details.
-Michael J. Sullivan

Mypy 0.760 released

17 December 2019: Mypy 0.760 was released. This release includes various fixes and improvements, and a
type signature suggestion feature for tools.
Read the
blog post
for the details.
-Jukka Lehtosalo

Older news

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.

Read More

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