ruff/docs/rules/prefix-type-params.md

prefix-type-params (PYI001)

Derived from the flake8-pyi linter.

What it does

Checks that type TypeVar, ParamSpec, and TypeVarTuple definitions in stubs are prefixed with _.

Why is this bad?

By prefixing type parameters with _, we can avoid accidentally exposing names internal to the stub.

Example

from typing import TypeVar

T = TypeVar("T")

Use instead:

from typing import TypeVar

_T = TypeVar("_T")