Talks - Charlie Marsh: Ruff: An Extremely Fast Python Linter and Code Formatter, Written in Rust

Ruff is an extremely fast Python linter and code formatter written in Rust, processing Python code significantly faster than traditional tools

Performance improvements came from multiple optimizations:

• Using byte offsets instead of row/column indexing
• Small integer optimizations to avoid heap allocations
• Avoiding regular expressions for common operations
• Parallel processing of files
• Single-pass analysis versus multiple tool passes

Key architectural decisions:

• Hand-written parser instead of generated parser for better control
• Stack vs heap memory usage optimization
• SIMD and data parallelism
• Common intermediate representation for all rules
• Focus on avoiding unnecessary allocations

Data-driven approach to optimization:

• Continuous benchmarking on real codebases
• Profiling to identify bottlenecks
• Making optimization decisions based on measured data
• Testing against large real-world projects

Success metrics:

• Over 18 million downloads per month
• Used by major Python projects like FastAPI, Pandas, SciPy
• 2x performance improvement over the past year
• Half a million VS Code extension installs
• 27,000+ GitHub stars

Key principles:

• Performance as a first-class concern
• Data-driven decision making
• Balance between optimization and maintainability
• Investment in tooling and benchmarking
• Focus on end-user experience over pure performance gains