import os
# Preferred - no KeyError exceptions even if no default value given
os.getenv('KEY','default value')# Alternate - NOTE: KeyError exception If a key is NOT present
os.environ['KEY']# To avoid KeyError exceptions when using os.environ :
os.environ.get('KEY_THAT_MIGHT_EXIST')# Returns `None` if key doesn't exist
os.environ.get('KEY_THAT_MIGHT_EXIST', default_value)# Returns `default_value` if key doesn't exist