Shared dependencies in FastAPI - Mini Project: Build & Apply

Using Shared Dependencies in FastAPI

📖 Scenario: You are building a simple web API with FastAPI. You want to reuse a common dependency that provides a database connection object for multiple API endpoints.

🎯 Goal: Create a FastAPI app that uses a shared dependency function to provide a database connection string to two different endpoints.

📋 What You'll Learn

Create a dependency function called get_db that returns the string 'db_connection'.

Create a FastAPI app instance called app.

Create two GET endpoints: /items/ and /users/.

Both endpoints must use the get_db dependency to receive the database connection string.

Each endpoint should return a JSON response with a key db and the value from the dependency.

💡 Why This Matters

🌍 Real World

Shared dependencies in FastAPI help avoid repeating code for common resources like database connections, authentication, or configuration.

💼 Career

Understanding shared dependencies is essential for building scalable and maintainable APIs in professional FastAPI development.

1

Create the shared dependency function

Create a function called get_db that returns the string 'db_connection'.

FastAPI

# Your code here

Need a hint?

Define a simple function named get_db that returns the string 'db_connection'.

2

Create the FastAPI app instance

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

FastAPI

def get_db():
    return 'db_connection'

# Your code here

Need a hint?

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

3

Create the /items/ endpoint using the shared dependency

Create a GET endpoint /items/ using @app.get("/items/"). Add a parameter db that uses Depends(get_db). Return a dictionary with key db and value db.

FastAPI

from fastapi import FastAPI
from fastapi import Depends

def get_db():
    return 'db_connection'

app = FastAPI()

# Your code here

Need a hint?

Use @app.get("/items/") and a function with parameter db: str = Depends(get_db). Return {"db": db}.

4

Create the /users/ endpoint using the shared dependency

Create a GET endpoint /users/ using @app.get("/users/"). Add a parameter db that uses Depends(get_db). Return a dictionary with key db and value db.

FastAPI

from fastapi import FastAPI
from fastapi import Depends

def get_db():
    return 'db_connection'

app = FastAPI()

@app.get("/items/")
def read_items(db: str = Depends(get_db)):
    return {"db": db}

# Your code here

Need a hint?

Repeat the pattern from the previous step for the /users/ endpoint.