Environment-based settings in FastAPI - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

How does FastAPI behave with environment-based settings?

Given a FastAPI app that loads settings from environment variables using Pydantic's BaseSettings, what will be the output when accessing the `/info` endpoint if the environment variable `APP_MODE` is set to `production`?

FastAPI

from fastapi import FastAPI
from pydantic import BaseSettings

class Settings(BaseSettings):
    app_mode: str = "development"

    class Config:
        env_prefix = "APP_"

settings = Settings()
app = FastAPI()

@app.get("/info")
async def get_info():
    return {"mode": settings.app_mode}

A {"mode": "production"}

B {"mode": "development"}

C {"mode": "APP_production"}

D {"mode": null}

💡 Hint

Remember that Pydantic BaseSettings reads environment variables with the prefix defined in Config.

The Settings class uses env_prefix 'APP_', so it looks for environment variable 'APP_MODE'. If set to 'production', settings.app_mode will be 'production'.

📝 Syntax

intermediate

Identify the syntax error in environment settings loading

Which option contains a syntax error when defining environment-based settings with Pydantic in FastAPI?

FastAPI

from pydantic import BaseSettings

class Config(BaseSettings):
    database_url: str

    class Config:
        env_prefix = "DB_"

A

class Settings(BaseSettings):
    database_url: str

    class Config:
        env_prefix = "DB_"

B

class Settings(BaseSettings):
    database_url: str

    class Config:
        env_prefix = DB_

C

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D

class Settings(BaseSettings):
    database_url: str

    class Config:
        env_prefix = 'DB_'

💡 Hint

Check how string values are assigned in Python.

Option B misses quotes around DB_, causing a NameError or SyntaxError because DB_ is undefined.

❓ state_output

advanced

What is the value of settings after loading multiple environment variables?

Consider this settings class and environment variables set as `APP_MODE=testing` and `APP_DEBUG=true`. What will be the value of `settings.debug` and `settings.app_mode`?

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    app_mode: str = "production"
    debug: bool = False

    class Config:
        env_prefix = "APP_"

settings = Settings()

A settings.app_mode == 'production' and settings.debug == True

B settings.app_mode == 'production' and settings.debug == False

C settings.app_mode == 'testing' and settings.debug == False

D settings.app_mode == 'testing' and settings.debug == True

💡 Hint

Boolean environment variables are parsed by Pydantic automatically.

Pydantic reads APP_MODE and APP_DEBUG from environment, converting 'true' to True boolean.

🔧 Debug

advanced

Why does the FastAPI app not reflect updated environment variables?

A developer changes environment variables after the FastAPI app has started but the app still shows old settings values. What is the most likely reason?

A FastAPI caches environment variables internally and ignores changes.

B Environment variables cannot be changed after Python starts.

C Settings are loaded once at app startup and not reloaded dynamically.

D Pydantic BaseSettings automatically reloads environment variables on each request.

💡 Hint

Think about when the settings object is created and how environment variables are read.

Settings instance is created once at startup, so changes to environment variables after that won't affect the running app.

🧠 Conceptual

expert

Which approach ensures secure environment-based settings in FastAPI?

To keep sensitive data like API keys secure and configurable per environment, which practice is best when using FastAPI with environment-based settings?

A Use environment variables loaded from a secure .env file and never commit it to version control.

B Hardcode secrets in the settings class as default values for easy access.

C Store secrets in the source code but encrypt them with a custom algorithm.

D Pass secrets as query parameters in API requests to the FastAPI app.

💡 Hint

Think about common security best practices for managing secrets.

Using environment variables and .env files excluded from version control is a standard secure practice.