Environment-based settings in FastAPI - Mini Project: Build & Apply

Environment-based settings in FastAPI

📖 Scenario: You are building a simple FastAPI application that needs to use different settings depending on the environment it runs in, such as development or production.This is like having different light switches for day and night: you want the app to behave differently without changing the main code.

🎯 Goal: Create a FastAPI app that loads settings from environment variables using pydantic.BaseSettings. You will define a settings class, set a default environment, and use the settings in a route.

📋 What You'll Learn

Create a Settings class inheriting from pydantic.BaseSettings with a debug boolean field

Add a ENVIRONMENT variable to specify the environment name

Load the settings and use the debug value in a FastAPI route response

💡 Why This Matters

🌍 Real World

Many web applications need to behave differently in development, testing, and production. Using environment-based settings helps keep code clean and secure.

💼 Career

Understanding environment-based configuration is essential for backend developers working with FastAPI or any modern web framework.

1

Create the Settings class

Create a class called Settings that inherits from pydantic.BaseSettings. Add a boolean field called debug with a default value False.

FastAPI

from pydantic import BaseSettings

# Create Settings class with debug field
# Your code here

Need a hint?

Use class Settings(BaseSettings): and define debug: bool = False inside.

2

Add environment variable for environment name

Add a variable called ENVIRONMENT and set it to the string 'development'.

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    debug: bool = False

# Set environment variable
# Your code here

Need a hint?

Just write ENVIRONMENT = 'development' below the class.

3

Load settings and create FastAPI app

Import FastAPI from fastapi. Create a variable called settings by instantiating Settings(). Then create a FastAPI app instance called app.

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    debug: bool = False

ENVIRONMENT = 'development'

# Import FastAPI and create settings and app
# Your code here

Need a hint?

Use settings = Settings() and app = FastAPI() after importing.

4

Create a route using the settings

Add a GET route at / using @app.get("/"). Define a function called read_root that returns a dictionary with a key debug_mode and value from settings.debug.

FastAPI

from pydantic import BaseSettings
from fastapi import FastAPI

class Settings(BaseSettings):
    debug: bool = False

ENVIRONMENT = 'development'

settings = Settings()
app = FastAPI()

# Add GET route returning debug mode
# Your code here

Need a hint?

Use @app.get("/") and return {"debug_mode": settings.debug} inside the function.