Async generator dependencies in FastAPI - Mini Project: Build & Apply

Async Generator Dependencies in FastAPI

📖 Scenario: You are building a simple FastAPI app that needs to manage a resource using an async generator dependency. This pattern is useful for opening and closing connections or sessions cleanly.

🎯 Goal: Create an async generator dependency that yields a resource string, then use it in a FastAPI route to return the resource.

📋 What You'll Learn

Create an async generator function called get_resource that yields the string 'resource_opened'

Use yield inside get_resource to provide the resource

Create a FastAPI app instance called app

Create a GET route /resource that uses get_resource as a dependency

Return the yielded resource string from the route handler

💡 Why This Matters

🌍 Real World

Async generator dependencies are used in FastAPI to manage resources like database connections, sessions, or files that need setup and cleanup around a request.

💼 Career

Understanding async generator dependencies is important for backend developers working with FastAPI to write clean, efficient, and maintainable code that manages resources properly.

1

Create the async generator dependency

Create an async generator function called get_resource that yields the string 'resource_opened'.

FastAPI

# Your code here

Need a hint?

Use async def to define the function and yield to provide the resource.

2

Create the FastAPI app instance

Import FastAPI from fastapi and create an app instance called app.

FastAPI

async def get_resource():
    yield 'resource_opened'

# Your code here

Need a hint?

Use from fastapi import FastAPI and then app = FastAPI().

3

Create a GET route using the async generator dependency

Create a GET route /resource using @app.get("/resource"). Define an async function read_resource that takes a parameter resource with a dependency on get_resource using Depends. Return the resource string from the function.

FastAPI

from fastapi import FastAPI
from fastapi import Depends

async def get_resource():
    yield 'resource_opened'

app = FastAPI()

# Your code here

Need a hint?

Use @app.get("/resource") and Depends(get_resource) to inject the dependency.

4

Complete the FastAPI app with dependency injection

Ensure the full code includes the import of Depends, the async generator get_resource, the app instance app, and the GET route /resource that returns the yielded resource string.

FastAPI

from fastapi import FastAPI
from fastapi import Depends

async def get_resource():
    yield 'resource_opened'

app = FastAPI()

@app.get("/resource")
async def read_resource(resource: str = Depends(get_resource)):
    return resource

# Your code here if needed

Need a hint?

Check that all parts are included and correctly connected.