ruff/docs/rules/unused-variable.md

unused-variable (F841)

Derived from the Pyflakes linter.

Autofix is always available.

What it does

Checks for the presence of unused variables in function scopes.

Why is this bad?

A variable that is defined but not used is likely a mistake, and should be removed to avoid confusion.

If a variable is intentionally defined-but-not-used, it should be prefixed with an underscore, or some other value that adheres to the dummy-variable-rgx pattern.

Example

def foo():
    x = 1
    y = 2
    return x

Use instead:

def foo():
    x = 1
    return x