Todo API — Python Clean Architecture

A RESTful To-Do list API built with Python and FastAPI, following Clean Architecture principles with an in-memory database.

Architecture

todo/
├── entities/        Pure domain model (Todo)
├── interfaces/      Repository contract
├── usecases/        Business logic (CRUD)
└── infrastructure/  In-memory repository

Each layer has a single responsibility:

Layer	Responsibility
entities/	Pure domain model (Todo)
interfaces/	Repository contract
usecases/	Business logic (CRUD)
infrastructure/	In-memory repository

API Endpoints

Method	Endpoint	Description	Status
GET	/todos	List all todos	200
POST	/todos	Create a todo	201
GET	/todos/{id}	Get by ID	200
PUT	/todos/{id}	Update a todo	200
DELETE	/todos/{id}	Delete a todo	204

Todo Object

{
  "id": 1,
  "title": "Buy groceries",
  "completed": false,
  "created_at": "2026-03-12T11:00:00Z"
}

Requirements

• Python 3.9+

Setup & Run

pip install -r requirements.txt
uvicorn todo.main:app --port 8080 --reload

Server runs on http://localhost:8080.
Interactive docs: http://localhost:8080/docs

Testing

# Unit and functional tests
python -m pytest tests/ -v