Static Typing with Python

Guides

• Type System Guides
  • Typing Python Libraries
  • Writing and Maintaining Stub Files
  • Unreachable Code and Exhaustiveness Checking

Reference

• Type System Reference
  • Generics
  • Protocols and structural subtyping
  • Type Stubs
  • Typing Best Practices
  • Testing and Ensuring Type Annotation Quality
  • typing Module Documentation

See also

The documentation at https://mypy.readthedocs.io/ is relatively accessible and complete. Particularly refer to the “Type System Reference” section of the docs – since the Python typing system is standardised via PEPs, this information should apply to most Python type checkers.

Indices and tables

• Index

• Search Page

Discussions and Support

• User help forum

• User chat on Gitter

• Developer mailing list

Typing-related Tools

Type Checkers

• mypy, the reference implementation for type checkers.

• pyre, written in OCaml and optimized for performance.

• pyright, a type checker that emphasizes speed.

• pytype, checks and infers types for unannotated code.

Development Environments

• PyCharm, an IDE that supports type stubs both for type checking and code completion.

• Visual Studio Code, a code editor that supports type checking using mypy, pyright, or the Pylance extension.

Linters and Formatters

• black, a code formatter with support for type stub files.

• flake8-pyi, a plugin for the flake8 linter that adds support for type stubs.

Type-Hint and Stub Integration

• autotyping, a tool which infers simple types from their context and inserts them as inline type-hints.

• merge_pyi, integrates .pyi signatures as inline type-hints in Python source code. This is a thin wrapper around ApplyTypeAnnotationsVisitor from libCST.

Typing PEPs

https://peps.python.org/topic/typing

• PEP 482, literature overview on type hints

• PEP 483, background on type hints

• PEP 484, type hints

• PEP 526, variable annotations and ClassVar

• PEP 544, Protocol

• PEP 561, distributing typed packages

• PEP 563, from __future__ import annotations

• PEP 585, subscriptable generics in the standard library

• PEP 586, Literal

• PEP 589, TypedDict

• PEP 591, Final

• PEP 593, Annotated

• PEP 604, union syntax with |

• PEP 612, ParamSpec

• PEP 613, TypeAlias

• PEP 646, variadic generics and TypeVarTuple

• PEP 647, TypeGuard

• PEP 649 (draft), from __future__ import co_annotations

• PEP 655, Required and NotRequired

• PEP 673, Self

• PEP 675, LiteralString

• PEP 677 (rejected), (int, str) -> bool callable type syntax

• PEP 681 @dataclass_transform()

• PEP 688 Buffer

• PEP 692 Unpack[TypedDict] for **kwargs

• PEP 695 class Class[T]: type parameter syntax

• PEP 696 (draft), defaults for type variables

• PEP 698 @override

• PEP 702 (draft), @deprecated()

• PEP 705 (draft), TypedMapping