What is the use of python-dotenv?

Question

Need an example and please explain me the purpose of python-dotenv.
I am kind of confused with the documentation.

Answer 1

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"

Answer 2

If you're starting your app from a shell such as bash or zsh, then the point of .env management utilities like (npm) dotenv or python-dotenv becomes moot.

Here's an example of how to manage .env with bash that simply, directly, and safely addresses configuration as recommended by the 12-Factor App. It also requires no additional dependencies.

Given a project hosted under ~/projects/foobar/, create an environment file in a safe location outside your project's space (e.g. ~/.envs/foobar/dev). Its content may look something like this:

set -a

PROJECT=foobar
DB_NAME=foobar_dev
DB_PASSWORD=5ecret
CACHE_ENABLED=
DEBUG=yes
LOG=/tmp/foobar.log
...

set +a

Then create a symlink to that file from your project's space:

$ ln -s ~/.envs/foobar/dev ~/projects/foobar/.env

The project now has a .env file symlinking to the actual file. When you source the symlink, all variables between set -a and set +a are exported to the environment.

$ source ~/projects/foobar/.env

And voila! If you run python from the same shell instance you sourced the environment file, you can retrieve the latter and update your config with it:

import os
config.update(os.environ)

The point of making .env a symlink to ~/.envs/foobar/dev is an added precaution to listing it in .gititgnore. If for whatever reasons the file were to be checked into version control, its contents would just show that it's a link to another file.

Answer 3

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")

Answer 4

This answer is to elaborate on 1) what load_dotenv actually does under the hood, and 2) the relationship between the os.environ and the OS's environment variables.

As the accepted answer describes, we can store some keys & values in the .env file and load it using the load_dotenv; then the os.environ contains the key-value pairs in the .env file.

Does this mean invoking load_dotenv added an OS environment variable? - No.

Actually, what load_dotenv does is quite the same as os.environ['key'] = 'value'; see the source code.

But, os.environ['key'] = 'value' does not add this key&value as an OS environment variable; They are only valid while the Python script is running.

In other words, os.environ contains not only the OS environment variables but also one-time variables like these.

Answer 5

Adding to @cannin's answer, if you want to specify the which file you want to find:

from dotenv import find_dotenv
from dotenv import load_dotenv

env_file = find_dotenv(".env.dev")
load_dotenv(env_file)

Answer 6

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")