cosmic-python

Clean architecture in Python organizes code into four layers: models for domain logic, adapters for infrastructure, services for use-cases, and entrypoints for APIs or CLIs. This enforces dependency direction so high-level policies never depend on low-level implementations.

Start by creating a four-folder skeleton with models, adapters, services, and entrypoints directories. Implement a minimal domain model first, then build a service orchestrating a mock adapter, expose an entrypoint, and configure CI and testing tools to enforce boundaries.

Use unit tests for domain models, mocks for adapters, orchestrated tests for services, and contract tests for entrypoints. This layered testing strategy maintains architectural boundaries and ensures high-level use-case logic remains isolated from infrastructure changes.

Yes, applying clean architecture requires only a Python-friendly toolchain with standard testing tooling and no exotic dependencies. You can incrementally refactor existing systems by introducing the four-layer structure and dependency injection to improve maintainability.

You should avoid clean architecture for small, simple Python scripts or prototypes where strict layered boundaries, dependency injection, and rigorous testing discipline introduce unnecessary overhead and reduce development speed.