FastAPI From Zero

Learn the modern Python API framework the way it's actually used: type-hint-driven routing, Pydantic models and automatic validation, response models, the Depends() dependency system, async and concurrency done right, databases, authentication with OAuth2/JWT, testing, and deployment. Plus the killer feature — automatic interactive docs — explained, not just shown.

1. What FastAPI Is & Your First App FastAPI is a modern async Python framework where your type hints become validation, docs, and serialization all at once. Install it, write a five-line app, run it, and watch the interactive docs appear for free.
2. Path Operations & Parameters How routes work in FastAPI: the decorator picks the HTTP method and path, path and query parameters come from your function signature, and the type hints parse and validate everything for free.
3. Pydantic Models & Validation Pydantic turns a class of typed fields into a runtime gate that validates and coerces incoming data — and it's pure Python, so you can run it right here. It's the engine behind FastAPI request bodies and automatic 422 errors.
4. Response Models & Status Codes Shape what your endpoints return with response_model, split input from output models so clients can't set or see internal fields, and return honest HTTP status codes including clean 404s via HTTPException.
5. Dependency Injection with Depends() FastAPI's Depends() lets an endpoint declare what it needs and have the framework supply it — pagination, DB sessions, auth — as plain reusable functions, with yield for setup/teardown.
6. Async & Concurrency How FastAPI's event loop serves many requests on one thread, when to write async def vs plain def, and the #1 performance bug — blocking the event loop with a sync call inside async def.
7. Databases with SQLModel Make the get_db yield-dependency real with SQLModel — one class that's both your Pydantic model and your table — and wire create, read, update, and delete into the Book endpoints.
8. Authentication & Security Protect your Book API the FastAPI way: hash passwords, issue JWT access tokens from an OAuth2 password flow, and gate endpoints with a get_current_user dependency — plus the security must-knows.
9. Testing & Project Structure Test FastAPI in-process with TestClient, swap real dependencies for fakes via dependency_overrides, and grow past one giant main.py with APIRouter and a sane project layout.
10. Production & Where to Go Next You can build a validated, authenticated, tested, DB-backed FastAPI API. Now deploy it with uvicorn/gunicorn behind a proxy, learn background tasks, dodge the async pitfalls, and pick your next build.