Async generator dependencies in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an async generator dependency in FastAPI?

An async generator dependency is a function that uses async and yield to provide a resource, like a database session, and then clean it up after use. It allows setup and teardown around a request.

beginner

How do you define an async generator dependency in FastAPI?

You define it as an async function that uses yield to provide a value. After the yield, you put cleanup code that runs after the request finishes.

intermediate

Why use async generator dependencies instead of normal functions in FastAPI?

Because async generator dependencies let you run code before and after a request asynchronously, like opening and closing a database connection safely.

beginner

What happens after the yield statement in an async generator dependency?

The code after yield runs after the request is done. It usually cleans up resources like closing connections or files.

beginner

Can async generator dependencies be used with FastAPI's Depends function?

Yes, you use Depends to declare async generator dependencies in your path operation functions. FastAPI handles calling and cleanup automatically.

What keyword is used to provide a value in an async generator dependency?

A yield

B return

C await

D async

The yield keyword provides the value and pauses the function until cleanup is needed.

What does FastAPI do after the yield in an async generator dependency?

A Ignores the rest of the function

B Starts a new request

C Runs cleanup code

D Returns the value again

FastAPI runs the code after yield to clean up resources after the request.

Why use async generator dependencies in FastAPI?

A To manage resources with setup and cleanup

B To speed up the server startup

C To avoid using async functions

D To block other requests

They help manage resources like database connections safely during requests.

How do you declare an async generator dependency in a path operation?

A Using a global variable

B Using Depends with the async generator function

C Using return statement

D Using a class

You use Depends to tell FastAPI to use the async generator dependency.

Can async generator dependencies run synchronous code after yield?

A Only if decorated

B No, it must be async only

C No, it must be sync only

D Yes, cleanup code can be sync or async

Cleanup code after yield can be synchronous or asynchronous.

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

Think about setup and teardown around a request.

Describe a real-life example where you would use an async generator dependency in FastAPI.

Imagine opening and closing a door for each visitor.