MonkeyType is a Python library and CLI tool that collects runtime types of function arguments and return values using Python's sys.setprofile hook. It stores these call traces (default SQLite) and can generate PEP 484 stub files or directly apply type annotations to source code via libcst. The architecture separates tracing (CallTracer), storage (CallTraceStore interface with SQLite implementation), stub generation (FunctionDefinition, ModuleStub), and application (libcst-based code transformation). It provides a configurable plugin system (Config/DefaultConfig) for customizing trace storage, code filtering, sampling, and type rewriting. The type rewriting subsystem includes a GenericTypeRewriter visitor pattern and several built-in rewriters (RemoveEmptyContainers, RewriteConfigDict, RewriteLargeUnion, RewriteMostSpecificCommonBase, RewriteGenerator) that refine raw union types into more idiomatic annotations. The project is well-tested with a comprehensive test suite and has been used in production at Instagram.
This repository is an awesome list curating resources for Python typing, including static and dynamic type checkers, stub packages, additional types, backports, tools, integrations, and articles. It does not function as a traditional software application but serves as a static reference guide. The repository includes minimal tooling for maintenance: a package.json defining an npm script to run awesome-lint for list formatting, a GitHub Actions workflow to automate linting on pushes and pull requests, and Dependabot configuration to keep dependencies updated. The primary value lies in the meticulously organized README.md, which categorizes and links to numerous Python typing projects. While the repository lacks reusable software components, it demonstrates good practices in project maintenance through automated linting and dependency updates. The technical drift is low due to active dependency monitoring, and the project is maintained with recent commits and issue activity.