Ruff

Last updated: Mar 5, 2026

Rationale

We use Ruff  to lint and format Python source code.

Ruff allows us to achieve the following:

• Lint Python files in an extremely fast fashion  with hundreds of rules  inherited from other linters like pyflakes, flake8, and pylint, among others. Such rules were reimplemented using Rust.
• Format  Python files based on Black  rules for consistency.
• Cache  already-reviewed files for performance.
• Integrate in-editor linting and formatting using its VS Code extension  for the development experience.

Alternatives

Below are alternatives we have used in the past that were replaced by Ruff.

Prospector

• Prospector  is a meta-linter that incorporates other linters like pylint, pycodestyle and McCabe complexity.
• It does not do anything else besides incorporating external linters in a unified interface.
• It supports fewer rules  when compared to Ruff and does not support formatting.
• It is much slower compared to Ruff.
• It does not provide any formatting capabilities.
• It does not seem to provide caching mechanisms.
• It does not have an official VS Code extension.

Black

• Black  is a Python source code formatter.
• It does not do anything else besides formatting Python code.
• It does not support any linting rules as it is only a formatter.
• It is similar to Ruff in terms of formatting performance.
• It provides the same formatting capabilities as Ruff.
• It provides caching mechanisms  for performance.
• It has an official VS Code extension .

SonarQube

• SonarQube  is a SaaS source code linter.
• It supports linting for several languages  and also other features like code coverage and SCA.
• It does not seem to publish which rules it supports for Python.
• It is much slower compared to Ruff and Prospector.
• It does not provide any formatting capabilities.
• Although it provides cache mechanisms , we found that they actually made the tool slower.
• Although it has an official VS Code extension , we found it was very slow and affected the development experience.

Usage

We use Ruff for linting and formatting all of Fluid Attacks’ Python source code.