Environment-based configuration in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Flask app configuration?

Given this Flask app code, what will be the value of app.config['DEBUG'] when FLASK_ENV is set to production?

Flask

import os
from flask import Flask

app = Flask(__name__)

if os.getenv('FLASK_ENV') == 'development':
    app.config['DEBUG'] = True
else:
    app.config['DEBUG'] = False

print(app.config['DEBUG'])

A True

B Raises KeyError

C None

D False

💡 Hint

Think about what happens when the environment variable is not 'development'.

The code sets DEBUG to True only if FLASK_ENV is 'development'. For 'production', DEBUG is set to False.

📝 Syntax

intermediate

Which option correctly loads environment variables into Flask config?

Which code snippet correctly loads environment variables from a .env file into a Flask app configuration using python-dotenv?

A

from dotenv import load_dotenv
load_dotenv()
app.config.from_envvar('MY_CONFIG')

B

from dotenv import load_dotenv
load_dotenv()
app.config.from_prefixed_env('MYAPP_')

C

from dotenv import load_dotenv
load_dotenv()
app.config.from_mapping(os.environ)

D

from dotenv import load_dotenv
load_dotenv()
app.config.from_object('config')

💡 Hint

Look for the method that accepts a dictionary of environment variables.

app.config.from_mapping(os.environ) loads all environment variables into Flask config.

❓ state_output

advanced

What is the value of app.config['DATABASE_URI'] after running this code?

Consider this Flask app configuration code snippet. What will be the value of app.config['DATABASE_URI'] if the environment variable DATABASE_URI is not set?

Flask

import os
from flask import Flask

app = Flask(__name__)
app.config['DATABASE_URI'] = os.getenv('DATABASE_URI', 'sqlite:///default.db')

print(app.config['DATABASE_URI'])

A 'sqlite:///default.db'

B None

C Raises KeyError

D Empty string ''

💡 Hint

Check the second argument of os.getenv.

os.getenv returns the default value if the environment variable is not set.

🔧 Debug

advanced

Why does this Flask app fail to load environment config?

This Flask app tries to load config from environment variables but fails. What is the error in this code?

Flask

import os
from flask import Flask

app = Flask(__name__)
app.config.from_envvar('MYAPP_SETTINGS')

# Assume MYAPP_SETTINGS is set to 'config.py' file path

A The config file path must be absolute, relative paths cause failure

B MYAPP_SETTINGS must be a Python module, not a file path

C from_envvar expects the environment variable to contain a file path to a config file, so this is correct

D The config file must be imported with importlib before calling from_envvar

💡 Hint

Check how Flask expects config file paths in from_envvar.

Flask's from_envvar requires the environment variable to point to an absolute path to the config file.

🧠 Conceptual

expert

Which statement about Flask environment-based configuration is correct?

Select the correct statement about managing Flask app configuration using environment variables.

A Flask requires restarting the server to detect changes in environment variables

B Using app.config.from_object() allows switching configs by passing different config classes

C Environment variables cannot override values set in config.py files

D Flask automatically loads .env files without any code when FLASK_ENV is set

💡 Hint

Think about how Flask config classes work.

app.config.from_object() lets you load different config classes for different environments easily.