python – How to access environment variable values

python – How to access environment variable values

Environment variables are accessed through os.environ

import os
print(os.environ[HOME])

Or you can see a list of all the environment variables using:

os.environ

As sometimes you might need to see a complete list!

# using get will return `None` if a key is not present rather than raise a `KeyError`
print(os.environ.get(KEY_THAT_MIGHT_EXIST))

# os.getenv is equivalent, and can also give a default value instead of `None`
print(os.getenv(KEY_THAT_MIGHT_EXIST, default_value))

The Python default installation location on Windows is C:Python. If you want to find out while running python you can do:

import sys
print(sys.prefix)

To check if the key exists (returns True or False)

HOME in os.environ

You can also use get() when printing the key; useful if you want to use a default.

print(os.environ.get(HOME, /home/username/))

where /home/username/ is the default

python – How to access environment variable values

The original question (first part) was how to check environment variables in Python.

Heres how to check if $FOO is set:

try:  
   os.environ[FOO]
except KeyError: 
   print Please set the environment variable FOO
   sys.exit(1)