Python Fastapi Todo App

Skill: Python FastAPI Todo App

Creates a simple Todo API with FastAPI, SQLite, and basic CRUD operations.

When to use

When the user asks to create a todo app, task manager API, or simple REST API with Python.

Steps

First, make sure Python 3.11+ is installed. On macOS use brew install python@3.11, on Linux use apt-get install python3.11.

Create the project directory and initialize a virtual environment:

mkdir -p todo-api/app
cd todo-api
python3 -m venv venv
source venv/bin/activate

Install the dependencies:

pip install fastapi uvicorn sqlalchemy

Create the file app/database.py:

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

DATABASE_URL = "sqlite:///./todos.db"

engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

Create the file app/models.py:

from sqlalchemy import Column, Integer, String, Boolean
from .database import Base

class Todo(Base):
    __tablename__ = "todos"

    id = Column(Integer, primary_key=True, index=True)
    title = Column(String, index=True)
    description = Column(String, default="")
    completed = Column(Boolean, default=False)

Create app/main.py with the FastAPI app, including these endpoints:

• GET /todos — list all todos
• POST /todos — create a new todo
• PUT /todos/{id} — update a todo
• DELETE /todos/{id} — delete a todo

The app should read $API_HOST and $API_PORT from the environment for the server bind address.

Add the project conventions to AGENTS.md at the root (Codex reads AGENTS.md for persistent project context).

Test the API:

curl http://localhost:8000/todos

curl -X POST http://localhost:8000/todos -H "Content-Type: application/json" -d '{"title": "Buy milk", "completed": false}'

For each endpoint, run a quick smoke test to make sure it returns 200.

Notes

• Keep it simple, no auth needed
• Use SQLite so there's no external database dependency
• Add a .env with API_HOST=0.0.0.0 and API_PORT=8000