Reading in environment variables from an environment file

Question

I use Python Dotenv Library. Just install the library pip install python-dotenv, create a .env file with your environment variables, and import the environment variables in your code like this:

import os
from dotenv import load_dotenv

load_dotenv()

MY_ENV_VAR = os.getenv('MY_ENV_VAR')

From the .env file:

MY_ENV_VAR="This is my env var content."

This is the way I do when I need to test code outside my docker system and prepare it to return it into docker again.

If your system/environment/workflow supports using shell scripts, you can create a script that wraps these 2 operations:

1. Sourcing the .env file and exporting them as environment variables
   • Using the set -a option where "Each variable or function that is created or modified is given the export attribute and marked for export to the environment of subsequent commands".
2. Calling your Python script/app that has plain os.environ.get code

Sample .env file (config.env):

TYPE=prod
PORT=5000

Sample Python code (test.py):

import os

print(os.environ.get('TYPE'))
print(os.environ.get('PORT'))

Sample bash script (run.sh):

#!/usr/local/bin/bash

set -a
source config.env
set +a

python3 test.py

Sample run:

$ tree
.
├── config.env
├── run.sh
└── test.py

$ echo $TYPE

$ echo $PORT

$ python3 test.py
None
None

$ ./run.sh 
prod
5000

When you run the Python script directly (python3 test.py) without source-ing the .env file, all the environ.get calls return None.

But, when you wrap it in a shell script that first loads the .env file into environment variables, and then runs the Python script afterward, the Python script should now be able to read the environment variables correctly.

As compared with the other popular answer, this doesn't need any external Python libraries.

This could also work for you:

env_vars = [] # or dict {}
with open(env_file) as f:
    for line in f:
        if line.startswith('#') or not line.strip():
            continue
        # if 'export' not in line:
        #     continue
        # Remove leading `export `, if you have those
        # then, split name / value pair
        # key, value = line.replace('export ', '', 1).strip().split('=', 1)
        key, value = line.strip().split('=', 1)
        # os.environ[key] = value  # Load to local environ
        # env_vars[key] = value # Save to a dict, initialized env_vars = {}
        env_vars.append({'name': key, 'value': value}) # Save to a list

print(env_vars)

In the comments, you'll find a few different ways to save the env vars and also a few parsing options i.e. to get rid of the leading export keyword. Another way would be to use the python-dotenv library. Cheers.

You can use ConfigParser. Sample example can be found here.

But this library expects your key=value data to be present under some [heading]. For example, like:

[mysqld]
user = mysql  # Key with values
pid-file = /var/run/mysqld/mysqld.pid
skip-external-locking
old_passwords = 1
skip-bdb      # Key without value
skip-innodb