SQLALCHEMY_DATABASE_URL = "sqlite:///./test.db" engine = create_engine(SQLALCHEMY_DATABASE_URL) SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine) Base = declarative_base()
from fastapi.testclient import TestClient from main import app
: Generates interactive API docs automatically using Swagger UI and ReDoc .
# PUT endpoint to update an existing item @app.put("/items/item_id") def update_item(item_id: int, item: Item): for existing_item in items: if existing_item["id"] == item_id: existing_item["name"] = item.name existing_item["description"] = item.description return existing_item return "error": "Item not found"
FastAPI is a modern, fast (high-performance) web framework for building APIs with Python 3.7+. fastapi tutorial pdf
You now have a production-ready knowledge base to build APIs with FastAPI. Save this document as PDF and keep it as your go-to reference.
You'll also need to install an ASGI server like uvicorn:
FastAPI makes it easy to capture data from the URL path or query string. Path Parameters
: Increases development speed by roughly 200% to 300%. Fewer Bugs : Reduces developer-induced errors by about 40%. SQLALCHEMY_DATABASE_URL = "sqlite:///
This code creates a basic FastAPI application with a single endpoint at / .
FastAPI leverages Python type hints to perform data validation, serialization, and documentation automatically.
from typing import Optional, Union
: Accessible at http://127.0.0 . It provides an interactive interface to test your API endpoints directly from the browser. Save this document as PDF and keep it
Before diving into code, let's understand the "why." FastAPI solves three fundamental problems that plagued previous Python frameworks like Flask and Django (for API development):
@app.get("/items/") async def list_items(skip: int = 0, limit: int = 10): return "skip": skip, "limit": limit
This is where FastAPI truly shines. Now, visit http://127.0.0.1:8000/docs . You'll see the automatically generated Swagger UI, which provides an interactive interface to explore and test your API endpoints. Similarly, you can visit http://127.0.0.1:8000/redoc for alternative, ReDoc-style documentation.