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 QWEN.md at the root (Qwen Code reads QWEN.md, and also 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