Environment variables are a powerful way to configure applications, offering benefits such as deploying without code changes, ensuring secrets are not leaked into source code, and abstracting config and secret supply. In Python, environment variables can be accessed using the `os.environ` object, which acts like a dictionary but has limitations. To get an environment variable, you can access it directly, use the `get()` method with a default value, or check for its existence without caring about its value. You can set environment variables in Python just like setting keys on a dictionary, and there are libraries available to parse `.env` files and populate the `os.environ` object, but these have drawbacks such as security issues and difficulties with managing them across environments. A more recommended approach is using a centralized config solution like Doppler, which provides an access-controlled dashboard for managing environment variables and offers benefits such as type checking and typecasting, making it easier to work with configuration values in your codebase.