What is the best way to manage environment variables in Python?

Managing environment variables is crucial for any application to ensure security, portability, and maintainability. In Python, environment variables are often used to keep sensitive information, like API keys or database passwords, away from the codebase, or to tailor application behavior based on the environment (e.g., development, testing, production).

1. `os` module: Python’s built-in `os` module allows you to access environment variables via `os.environ`. For instance, `os.environ.get(‘MY_VARIABLE’)` retrieves the value of `MY_VARIABLE` if it exists, or returns `None` otherwise.

2. `.env` files with `python-dotenv`: For local development, it’s common to use `.env` files to store environment variables. The `python-dotenv` package allows automatic loading of `.env` files, making local development smoother. Once installed with `pip install python-dotenv`, you can load your `.env` file with `load_dotenv()` at the start of your script or application. Then, access the variables using the `os` module as before.

3. Environment Configuration: In production or cloud environments (like AWS, Heroku, etc.), environment variables are often set through the platform’s specific tools or dashboards. Ensure your application correctly reads these variables as required.

4. Secrets Management Tools: For very sensitive data, consider using secrets management tools like HashiCorp’s Vault, AWS Secrets Manager, or Azure Key Vault. These tools offer an extra layer of security around sensitive information.

It’s crucial never to hard-code sensitive information directly in your Python applications. Instead, use environment variables and appropriate tools to manage them. Not only does this improve security by keeping secrets out of your codebase, but it also makes your applications more flexible and maintainable, as configuration can be changed without altering the code itself.