FastAPI / Basic: HTTP and typed boundaries

FastAPI β€” Basic: HTTP and typed boundaries

Build precise contracts for routes, inputs, models, responses, errors, and reusable dependencies.

6 lessons Β· No account required

What you will learn

  • Trace an in-process request through routing and validation.
  • Separate accepted input, public output, and domain failures.
  • Compose explicit request dependencies without hidden authority.

  1. ASGI, HTTP, and route selection

    Understand what FastAPI declares, what an ASGI server supplies, and how an in-process client verifies a complete HTTP contract.

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  2. Path, query, and type contracts

    Declare where values come from, how they are converted, and which bounds define a valid request.

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  3. Request bodies and Pydantic validation

    Turn JSON into a narrow validated command while distinguishing parsing, conversion, field constraints, and cross-field rules.

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  4. Responses, status, and serialization

    Define the public response independently from internal records and return HTTP semantics that match the completed operation.

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  5. Errors and validation boundaries

    Distinguish malformed requests, expected domain failures, and programming defects while keeping public errors stable and safe.

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  6. Dependencies and application composition

    Use dependency injection to declare reusable request context and owned resources without hiding security or mutable global state.

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