How is control flow implemented within the principles of clean architecture?

In clean architecture, the flow of control is organized so that dependencies point inward — from outer layers to inner layers. The main principles:

• Outer layers (interfaces, UI, infrastructure) call inner layers (business logic, domain), but not vice versa.
• The domain layer contains business rules and does not depend on implementation details.
• Layers interact through abstractions (interfaces), which makes it easy to replace implementations.

Flow example:

1. The user interacts with the UI (outer layer).
2. The UI calls a controller or application service.
3. The service accesses the domain layer, which contains business logic.
4. The domain layer may use repository interfaces to access data.
5. The implementation of repositories resides in the outer infrastructure layer.

This flow ensures loose coupling and high testability. In Python, this can be implemented through clear module separation and the use of abstract base classes (ABC) for interfaces.