Environment Variables

Applications often need configuration values such as API keys, database URLs, and secret keys.

Environment variables provide a secure and flexible way to manage these settings.

What are Environment Variables?

Environment variables are key–value pairs stored outside your code.

They allow you to configure your application without hardcoding sensitive information.

Why Environment Variables Matter

Without environment variables:

• Sensitive data may be exposed in code
• Configuration becomes hard to change
• Applications are less secure

With environment variables:

• Secrets are kept outside the codebase
• Configuration is flexible
• Applications are safer and easier to deploy

Example

Instead of writing this in your code:

You use an environment variable:

How They Work

Environment variables are set in your system and accessed by your application.

• The system stores the variable
• Your application reads it when needed

Setting Environment Variables

On macOS/Linux:

On Windows:

Using .env Files

In development, you can store variables in a .env file:

This file should not be committed to version control.

Best Practices

• Never hardcode secrets in your code
• Use environment variables for configuration
• Keep .env files private
• Use different values for development and production

Why This Matters

In real applications:

• Flask uses environment variables for configuration
• FastAPI apps rely on environment-based settings
• Django uses environment variables for secrets and database configs

This is standard practice in professional development.

Summary

• Environment variables store configuration outside your code
• They improve security and flexibility
• They are essential for real-world applications

You’ve now completed your development setup.

In the next module, you’ll start building your first web application.