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Frameworks & web · #fastapi
FastAPI's lifespan context manager replaces deprecated on_event handlers for startup/shutdown. Learn how to share a single pooled httpx.AsyncClient across requests, wire it through dependency injection, and avoid common testing pitfalls.
Learn how to set up SQLAlchemy 2.0’s AsyncEngine and AsyncSession for non‑blocking database access in FastAPI, including a working example, verification steps, and key limitations.
FastAPI 422 responses mean Pydantic validation failed. This guide walks you through recognizing the error, diagnosing its cause, applying the right fix, and verifying the result—so you can resolve validation problems quickly and safely.
FastAPI’s <code>Depends</code> lets you decouple request handlers from resource acquisition. Learn how to write sync and async dependencies, test them with <code>TestClient</code>, and avoid common pitfalls like deep chains and circular imports.
Learn how to set up JWT‑based authentication in FastAPI using python‑jose, Pydantic models, and Depends. Follow a step‑by‑step guide that covers token creation, validation, protected routes, error handling, and secret management.
FastAPI's Depends system eliminates duplicated session and auth code across endpoints. A worked example shows yield-based cleanup, per-request caching, and how to verify both behaviors yourself.
FastAPI's BackgroundTasks runs work after the response in the same process. Here's when that's the right call, the scope-leak traps, how to observe it, and when to graduate to a real queue.
FastAPI's Depends system is where shared logic should live. Here's how yield-based dependencies, scoping, and sync-vs-async choices work in practice — and where the pattern breaks down.
Learn how to spot why a FastAPI dependency’s cleanup code (after `yield`) never runs, and follow ordered checks to fix it.
python
sqlalchemy