Environment Variables

Environment variables are dynamic, user-definable values that can influence the behavior of running processes on a computer. They serve as a means to configure applications without altering the underlying code, enabling flexibility and adaptability in software development. Basically is a KEY=VALUE pair.

There are two types of environment variables:

• Regular environment variables
• System environment variables (can be user specific or public)

PATH Variable

The PATH environment variable is a list of directories that the operating system searches to find executable files when you enter a command.

• On Unix-like systems, directories are separated by colons (:)
• On Windows, they are separated by semicolons (;)
• Order matters, the system checks directories from left to right, executing the first match it finds

Interacting via Python

import os
 
 
# retrieve a variable
value = os.environ["VARIABLE_NAME"]  # raises KeyError if not found
value = os.environ.get("VARIABLE_NAME", "default_value")  # returns "default_value" if not found
 
# set or modify environment variables
os.environ["NEW_VARIABLE"] = "value"

Alternatively, for local development, it’s common to store environment variables in a .env file. This file contains key-value pairs and can be loaded into the application using the python-dotenv library.

Code Snippets

Linux / Mac OS

# create new environment variable
export MY_VAR=1
 
# show environment variable value
echo $MY_VAR
printenv MY_VAR
 
# show all environment variables
printenv
 
# adding new path to PATH variable
export PATH=$PATH:/path/to/directory

Windows OS

# create new environment variable
set MY_VAR=1
 
# show environment variable value
echo %MY_VAR%
 
# show all environment variables
set
 
# adding new path to PATH variable
set PATH=%PATH%;C:\path\to\directory