python-project-structure

To structure a Python project with clear module boundaries, organize code by cohesive responsibilities and use a flat, scalable directory layout. Establish a top-level package with explicit public interfaces to improve readability and simplify maintenance.

The best way to define a public API in a Python package is by using the __all__ variable. Explicit __all__ usage controls exactly what is exposed to importers, simplifies imports, and keeps internal module details private.

To organize tests in a Python project with a flat layout, use a dedicated tests/ directory at the top level. This aligns with shallow directory hierarchies and scales cleanly as the project grows alongside your src/ package.

You should use a flat directory layout for small to medium Python codebases during initial setup, refactoring, or API design. Shallow hierarchies scale better as the project grows and align with packaging and testing requirements.

Your Python package imports internal modules unexpectedly because it lacks explicit public interface boundaries. Defining __all__ in your package initialization files restricts exposed names and prevents internal modules from leaking into the public API.

This project structure guidance targets small to medium Python codebases. While the flat layout and explicit module boundaries scale well, large enterprise systems may eventually require deeper nested package hierarchies for complex domain separation.