Building APIs with FastAPI · 12-day planAll days
Day 6 of 12 30 minDependsAnnotatedyield
Use FastAPI's dependency injection to share logic between endpoints - common query parameters, loading an object or failing with 404, checking a header - and to manage resources like database sessions with yield. Learn Annotated shortcuts, dependencies of dependencies, and applying dependencies to whole apps.
By the end of today you can
- Declare dependencies with Depends and reuse them across endpoints
- Use dependencies for shared parameters and "load or 404" logic
- Write dependencies with yield to set up and clean up resources
- Chain dependencies and reuse them with Annotated type aliases
- Apply dependencies to a whole app or a group of routes
What's inside
- 4 sections
- 3 diagrams and mind maps
- 4 code examples you can run
- 5-question quiz
- 1A first dependency
- 2Load it or 404
- 3Setup and cleanup with yield
- 4Dependencies of dependencies
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