Access environment variables in Python

David Y.

—May 15, 2023

The ProblemThe Problem

How do I access environment variables in Python?

The SolutionThe Solution

The Python os module contains a mapping object (similar to a dictionary) called environ that stores all environment variables and their values.

import os

print(os.environ) # show all environment variables and their values.

One way to access environment variables is to use os.environ like a dictionary. For example, os.environ['SHELL'] will contain the value of the SHELL environment variable. However, if the requested environment variable does not exist, trying to access it will raise a KeyError exception. Therefore, a safer way to do this is use the os.getenv function, which allows us to specify a default fallback value.

shell_ev = os.getenv('SHELL', '/bin/bash')

This code will store the value of the SHELL environment variable in shell_ev. If this environment variable does not exist, the string /bin/bash will be stored.