1. Introduction

Goal of the Tutorial

In this tutorial, we will learn how to manage environment variables in a production setting using Flask. Environment variables are an important aspect of web applications that securely store configuration settings.

Learning Outcomes

By the end of the tutorial, you will be able to:
- Understand what environment variables are
- Use environment variables in Flask applications
- Manage environment variables in a production environment

Prerequisites

• Basic knowledge of Python
• Familiarity with Flask web framework

2. Step-by-Step Guide

Environment variables are key-value pairs that are used to customize the system environment for your application. They can be used to store sensitive data like API keys, passwords, and other configuration settings.

In Flask, the configuration settings are typically stored in files, but in a production environment, it's more secure and scalable to use environment variables.

Setting Environment Variables

In a Unix-based system, you can set an environment variable using the export command as follows:

export VARIABLE_NAME="Variable Value"

In Windows, you can use the set command:

set VARIABLE_NAME="Variable Value"

Accessing Environment Variables in Flask

In Flask, you can access these variables using os.environ or Flask's config object. For instance:

import os
from flask import Flask

app = Flask(__name__)
app.config['SECRET_KEY'] = os.environ.get('SECRET_KEY')

3. Code Examples

Example 1: Using os.environ

import os
from flask import Flask

app = Flask(__name__)
app.config['SECRET_KEY'] = os.environ.get('SECRET_KEY')

In this example, we're using os.environ.get('SECRET_KEY') to get the value of the SECRET_KEY environment variable that we've set in our system.

Example 2: Using Flask's config.from_pyfile

from flask import Flask

app = Flask(__name__)
app.config.from_pyfile('config.py')

In this example, we're loading the configuration from a Python file named config.py. This file contains the environment variables.

4. Summary

In this tutorial, we've learned what environment variables are, how to set them in our system, and how to use them in a Flask application. Our next step would be to learn how to manage these variables in a production environment, which involves different strategies and tools like Docker, Kubernetes, or cloud services.

5. Practice Exercises

1. Exercise 1: Set a new environment variable named DATABASE_URL with the value of your choice, then access it in a Flask application.
2. Exercise 2: Create a config.py file, then load it using Flask's config.from_pyfile method.

Solutions

1. Solution to Exercise 1:

# Set the environment variable
export DATABASE_URL="sqlite:///site.db"

# Access it in Flask
import os
from flask import Flask

app = Flask(__name__)
app.config['DATABASE_URL'] = os.environ.get('DATABASE_URL')

1. Solution to Exercise 2:

# config.py
SECRET_KEY = 'your-secret-key'
DATABASE_URL = 'sqlite:///site.db'

# Flask application
from flask import Flask

app = Flask(__name__)
app.config.from_pyfile('config.py')

In these exercises, you practiced setting and using environment variables in Flask. For further practice, try exploring different ways to manage these variables in a production environment.