What is the use of python-dotenv?

From the Github page:

Reads the key,value pair from .env and adds them to environment variable. It is great of managing app settings during development and in production using 12-factor principles.

Assuming you have created the .env file along-side your settings module.

.
├── .env
└── settings.py

Add the following code to your settings.py:

# settings.py
import os
from os.path import join, dirname
from dotenv import load_dotenv

dotenv_path = join(dirname(__file__), '.env')
load_dotenv(dotenv_path)

SECRET_KEY = os.environ.get("SECRET_KEY")
DATABASE_PASSWORD = os.environ.get("DATABASE_PASSWORD")

.env is a simple text file with each environment variable listed one per line, in the format of KEY="Value". The lines starting with # are ignored.

SOME_VAR=someval
# I am a comment and that is OK
FOO="BAR"

You could set the env variables like this:

 export PRIVATE_KEY=0X32323

and then read it with os module.

import os

private_key=os.getenv("PRIVATE_KEY")

But this way, environment variable works only for the duration that shell is live. If you close the shell and restart it, you have to set environmental variable again. python-dotenv prevents us from doing this repetitive work.For this create .env file and add variables in this format

 PRIVATE_KEY=fb6b05d6e75a93e30e22334443379292ccd29f5d815ad93a86ee23e749227

then in the file u want to access anv variables

import os
from dotenv import load_dotenv 

#default directory for .env file is the current directory
#if you set .env in different directory, put the directory address load_dotenv("directory_of_.env)
load_dotenv()

load_dotenv() will set the environment variables from .env and we access with os module

   private_key=os.getenv("PRIVATE_KEY")

In addition to @Will's answer, the python-dotenv module comes with a find_dotenv() that will try to find the .env file.

# settings.py
import os
from dotenv import load_dotenv, find_dotenv

load_dotenv(find_dotenv())

SECRET_KEY = os.environ.get("SECRET_KEY")
DATABASE_PASSWORD = os.environ.get("DATABASE_PASSWORD")