Sourcery vs mypy: Type Checking vs AI Refactoring (2026)

Quick Verdict Sourcery and mypy are not competing tools - they occupy entirely different positions in the Python code quality stack. mypy is a free, open-source static type checker that verifies Python type annotations at compile time, catching type errors before they become runtime exceptions. Sourcery is a paid, AI-powered code review and refactoring platform that integrates with GitHub and GitLab to review pull requests, suggest idiomatic Python improvements, and provide contextual feedback that no static analysis tool can generate. The comparison matters because Python teams frequently audit their quality toolchain and ask whether investing in AI code review makes sense when they already have type checking. The answer requires understanding that type correctness and code quality are orthogonal dimensions - fixing type errors does not improve code structure, and refactoring suggestions do not verify type annotations. Both tools address real gaps, and the most effective Python teams