Python | os.environ object

OS module in Python provides functions for interacting with the operating system. OS comes under Python’s standard utility modules. This module provides a portable way of using operating system dependent functionality.

os.environ in Python is a mapping object that represents the user’s environmental variables. It returns a dictionary having user’s environmental variable as key and their values as value.

os.environ behaves like a python dictionary, so all the common dictionary operations like get and set can be performed. We can also modify os.environ but any changes will be effective only for the current process where it was assigned and it will not change the value permanently.

Syntax: os.environ

Parameter: It is a non-callable object. Hence, no parameter is required

Return Type: This returns a dictionary representing the user’s environmental variables

Code #1: Use of os.environ to get access of environment variables

# Python program to explain os.environ object  
  
# importing os module  
import os 
import pprint 
  
# Get the list of user's 
# environment variables 
env_var = os.environ 
  
# Print the list of user's 
# environment variables 
print("User's Environment variable:") 
pprint.pprint(dict(env_var), width = 1) 

Output:

{'CLUTTER_IM_MODULE': 'xim',
 'COLORTERM': 'truecolor',
 'DBUS_SESSION_BUS_ADDRESS': 'unix:path=/run/user/1000/bus',
 'DESKTOP_SESSION': 'ubuntu',
 'DISPLAY': ':0',
 'GDMSESSION': 'ubuntu',
 'GJS_DEBUG_OUTPUT': 'stderr',
 'GJS_DEBUG_TOPICS': 'JS '
                     'ERROR;JS '
                     'LOG',
 'GNOME_DESKTOP_SESSION_ID': 'this-is-deprecated',
 'GNOME_SHELL_SESSION_MODE': 'ubuntu',
 'GTK_IM_MODULE': 'ibus',
 'HOME': '/home/ihritik',
 'IM_CONFIG_PHASE': '2',
 'JAVA_HOME': '/opt/jdk-10.0.1',
 'JOURNAL_STREAM': '9:28586',
 'JRE_HOME': '/opt/jdk-10.0.1/jre',
 'LANG': 'en_IN',
 'LANGUAGE': 'en_IN:en',
 'LESSCLOSE': '/usr/bin/lesspipe '
              '%s '
              '%s',
 'LESSOPEN': '| '
             '/usr/bin/lesspipe '
             '%s',
 'LOGNAME': 'ihritik',
 'PATH': '/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:
/usr/local/games:/snap/bin:/usr/local/java/jdk-10.0.1/bin:
/usr/local/java/jdk-10.0.1/jre/bin:/opt/jdk-10.0.1/bin:/opt/jdk-10.0.1/jre/bin',
 'PWD': '/home/ihritik',
 'QT4_IM_MODULE': 'xim',
 'QT_IM_MODULE': 'ibus',
 'SESSION_MANAGER': 'local/hritik:@/tmp/.ICE-unix/1127, unix/hritik:/tmp/.ICE-unix/1127',
 'SHELL': '/bin/bash',
 'SHLVL': '2',
 'SSH_AUTH_SOCK': '/run/user/1000/keyring/ssh',
 'TERM': 'xterm-256color',
 'TEXTDOMAIN': 'im-config',
 'TEXTDOMAINDIR': '/usr/share/locale/',
 'USER': 'ihritik',
 'USERNAME': 'ihritik',
 'VTE_VERSION': '4804',
 'WAYLAND_DISPLAY': 'wayland-0',
 'XDG_CONFIG_DIRS': '/etc/xdg/xdg-ubuntu:/etc/xdg',
 'XDG_CURRENT_DESKTOP': 'ubuntu:GNOME',
 'XDG_MENU_PREFIX': 'gnome-',
 'XDG_RUNTIME_DIR': '/run/user/1000',
 'XDG_SEAT': 'seat0',
 'XDG_SESSION_DESKTOP': 'ubuntu',
 'XDG_SESSION_ID': '2',
 'XDG_SESSION_TYPE': 'wayland',
 'XDG_VTNR': '2',
 'XMODIFIERS': '@im=ibus',
 '_': '/usr/bin/python3'}

Code #2: Accessing a particular environment variable

# Python program to explain os.environ object  
  
# importing os module  
import os 
  
# Get the value of 
# 'HOME' environment variable 
home = os.environ['HOME'] 
  
# Print the value of 
# 'HOME' environment variable 
print("HOME:", home) 
  
# Get the value of 
# 'JAVA_HOME' environment variable 
# using get operation of dictionary 
java_home = os.environ.get('JAVA_HOME') 
  
# Print the value of 
# 'JAVA_HOME' environment variable 
print("JAVA_HOME:", java_home) 

Output:

HOME: /home/ihritik
JAVA_HOME: /opt/jdk-10.0.1

Code #3: Modifying a environment variable

# Python program to explain os.environ object  
  
# importing os module  
import os 
  
  
# Print the value of 
# 'JAVA_HOME'  environment variable  
print("JAVA_HOME:", os.environ['JAVA_HOME') 
  
# Modify the value of 
# 'JAVA_HOME'  environment variable  
os.environ['JAVA_HOME'] = '/home / ihritik / jdk-10.0.1'
  
# Print the modified value of 
# 'JAVA_HOME' environment variable 
print("Modified JAVA_HOME:", os.environ['JAVA_HOME']) 

Output:

JAVA_HOME: /opt/jdk-10.0.1
Modified JAVA_HOME: /home/ihritik/jdk-10.0.1

Code #4: Adding a new environment variable

# Python program to explain os.environ object  
  
# importing os module  
import os 
  
# Add a new environment variable  
os.environ['GeeksForGeeks'] = 'www.geeksforgeeks.org'
  
# Get the value of 
# Added environment variable  
print("GeeksForGeeks:", os.environ['GeeksForGeeks']) 

Output:

GeeksForGeeks: www.geeksforgeeks.org

Code #5: Accessing a environment variable which does not exists

# Python program to explain os.environ object  
  
# importing os module  
import os 
  
# Print the value of 
# 'MY_HOME' environment variable  
print("MY_HOME:", os.environ['MY_HOME'] 
  
  
# If the key does not exists 
# it will produce an error 

Output:

Traceback (most recent call last):
  File "osenviron.py", line 8, in 
    print("MY_HOME:", os.environ['MY_HOME'])
  File "/usr/lib/python3.6/os.py", line 669, in __getitem__
    raise KeyError(key) from None
KeyError: 'MY_HOME'

Code #6: Handling error while Accessing a environment variable which does not exists

# Python program to explain os.environ object  
  
  
# importing os module  
import os 
  
# Method 1 
# Print the value of 
# 'MY_HOME' environment variable  
print("MY_HOME:", os.environ.get('MY_HOME', "Environment variable does not exist")) 
  
  
# Method 2 
try: 
    print("MY_HOME:", os.environ['MY_HOME']) 
except KeyError:  
    print("Environment variable does not exist") 

Output:

MY_HOME: Environment variable does not exist
Environment variable does not exist

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