Shared dependencies in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a shared dependency in FastAPI?

A shared dependency is a function or class that multiple path operations use to share common logic or data, like authentication or database sessions.

beginner

How do you declare a shared dependency in FastAPI?

You declare a shared dependency by creating a function and then including it in multiple path operations or other dependencies using the Depends parameter.

beginner

Why use shared dependencies in FastAPI?

Shared dependencies help avoid repeating code, keep logic centralized, and make your app easier to maintain and test.

intermediate

What happens if a shared dependency raises an exception?

If a shared dependency raises an exception, FastAPI stops processing the request and returns the error response immediately.

intermediate

Can shared dependencies depend on other dependencies in FastAPI?

Yes, shared dependencies can depend on other dependencies, allowing you to build complex dependency trees.

What FastAPI feature allows you to reuse logic across multiple routes?

A Background tasks

B Middleware

C Shared dependencies

D Event handlers

Shared dependencies let you reuse logic like authentication or database sessions across routes.

How do you include a shared dependency in a FastAPI path operation?

A By adding it as a parameter with Depends()

B By importing it in the route file

C By calling it inside the route function

D By registering it in middleware

You include shared dependencies by adding them as parameters with Depends() in the route function.

If a shared dependency raises an HTTPException, what does FastAPI do?

A Retries the dependency

B Returns the error response immediately

C Ignores the error and continues

D Logs the error but returns success

FastAPI stops processing and returns the error response immediately.

Can shared dependencies depend on other dependencies in FastAPI?

A Yes, dependencies can be nested

B No, dependencies must be independent

C Only if they are classes

D Only if they are async functions

FastAPI supports nested dependencies to build complex logic.

What is a benefit of using shared dependencies?

A Prevents error handling

B Makes the app slower

C Requires more code duplication

D Avoids repeating code and centralizes logic

Shared dependencies help avoid code repetition and centralize logic.

Explain how shared dependencies work in FastAPI and why they are useful.

Think about how you avoid repeating code in multiple routes.

Describe how you can handle errors raised in shared dependencies in FastAPI.

Consider what happens if a dependency fails.