FastAPI Tutorial: Building CRUD Endpoints with Pydantic and Dependency Injection

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A developer documenting a FastAPI learning project has completed Phase 2, adding real HTTP endpoints to an expense-tracking app that previously had a database but no way for users to interact with it. The phase covers implementing all four CRUD operations — Create, Read, Update, and Delete — using FastAPI's built-in Pydantic library for request and response validation. A key lesson was separating input and output into two distinct Pydantic schemas, preventing clients from supplying server-generated fields like IDs or timestamps. Dependency injection via FastAPI's Depends() function was also introduced to manage database sessions safely across all endpoints. The update required no new package installations, as Pydantic is already bundled with FastAPI.

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