How do I fix a codebase with extra tabs and newlines? #10012

Use the formatter for the mechanical whitespace cleanup, then the linter for policy checks:

ruff format .
ruff check --fix .
ruff format --check .
ruff check .

ruff format normalizes indentation, spacing, and blank-line layout in the same general style as Black. The lint pass handles fixable whitespace rules outside the formatter's scope. Running both check commands in CI prevents the changes from returning.

Two caveats: Ruff intentionally does not rewrite whitespace inside string literals, and it will preserve blank lines when removing them could change meaning or comments. If the “tabs” are literal characters embedded in generated data or multiline strings, a Python formatter should not touch them; use a targeted migration script and exclude generated files instead.

It is worth committing the formatting change separately from behavioral edits. That keeps blame and review manageable, especially when cleaning an existing codebase in one pass.