How do dependencies with `yield` manage resource lifetime in FastAPI?

Explains acquisition and cleanup around `yield`, including request and function scopes, streaming, and exception-safe ownership.

1Say itAnswer out loud first

2CompareCompare with Core answer

3RefineRefine with Stronger and Advanced

TL;DR

A dependency with yield acquires a resource before the yield, provides the yielded value to downstream dependencies or the handler, and runs the code after yield as cleanup. A try/finally or context manager makes cleanup run when processing succeeds or fails. In current FastAPI, request scope is the default and cleanup runs after the response is sent; scope="function" cleans up after the handler finishes but before the response is sent. The chosen scope must keep the resource alive for every consumer that still needs it.

Full answer below

Practice focus

Current FastAPI resource-lifetime knowledge and the judgment to align cleanup with actual resource use.

Answer first

Answer path

Core answer first, then checkpoints toward a stronger answer.

Start
Core answer
Start here. This is the direct spoken answer to practice first.
Overview
A yield dependency is a resource-owner boundary, so cleanup timing must match the response path.
A dependency with yield acquires a resource before the yield, provides the yielded value to downstream dependencies or the handler, and runs the code after yield as cleanup. A try/finally or context manager makes cleanup run when processing succeeds or fails. In current FastAPI, request scope is the default and cleanup runs after the response is sent; scope="function" cleans up after the handler finishes but before the response is sent. The chosen scope must keep the resource alive for every consumer that still needs it.

Review signals

Use these to catch weak phrasing, shallow reasoning, and risky claims.

Common mistakesCandidateCommon mistakesMistakes that weaken the answer or signal shallow understanding.Open details

Details

Assuming cleanup always runs immediately after the handler returns.
Using a function-scoped resource from a later stream.
Passing a yielded database session into background work.
Catching and silently swallowing downstream exceptions during cleanup.

How do dependencies with `yield` manage resource lifetime in FastAPI?

Practice focus

Answer path

Overview

Review signals

Follow-up prompts

Continue the section

Tech stacks

Skill areas

Suggest an improvement

Found this answer useful?