Use Pyright to check Python types

Cost

Open source. MIT licence, free to use in any project. Pylance, its editor extension, is not open source.

How to do it

Pyright 1.0 shipped in March 2019, and 1.1.414 came out in September 2026. PyPI counted over 11 million downloads of its wrapper in the week to 18 October 2026. It is MIT licensed and maintained by Microsoft. Choose something else when a framework needs a type plugin. mypy runs plugins for Django and Pydantic, but its 1.0 shipped only in February 2023. Run it on every change, as Use strict types and linters says.

Examples

Using these examples: they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

TOML example

# pyproject.toml
[tool.pyright]
include = ["src"]
typeCheckingMode = "strict"
pythonVersion = "3.13"

Python example

from dataclasses import dataclass

@dataclass(frozen=True)
class OrderLine:
    price: int
    qty: int

def total(lines: list[OrderLine]) -> int:
    return sum(line.price * line.qty for line in lines)

How to check

pyright exits 0 in the build, and pyproject.toml sets typeCheckingMode = "strict" for every new package.

Sources

• Pyright

Related rules

• Use Python for data work and as a second server language in Software choices
• Use strict types and linters in AI development