Let's first install the package that is going to take care of loading our virtual environment:

pip install python-dotenv

Then, in your settings.py:

import os
from dotenv import load_dotenv

load_dotenv()

The DEBUG variable:

DEBUG = os.getenv('DEBUG', 'True') == 'True'

Change the DEBUG environment variable from DEBUG=True to the code above. 

The code above will try to load an environment variable called DEBUG.

The comparison os.getenv('DEBUG') == 'True' compares the retrieved value with the string 'True'. This comparison will be True if the value of the DEBUG environment variable is 'True', and False otherwise.

The SECRET_KEY:

SECRET_KEY = os.getenv('SECRET_KEY', 'your-secret-key')

Note: Replace 'your-secret-key' with the secret key that previously existed in your django project.

The ALLOWED_HOSTS:

ALLOWED_HOSTS = os.getenv('ALLOWED_HOSTS', '127.0.0.1').split(',')

For the ALLOWED_HOSTS, if the environment variable is not set or is empty, the default value '' will be used. The split(',') method splits the value by commas and returns a list of host names.