os.getenv()

os.getenv(key, default=None)

Return the value of the environment variable key if it exists, or default if it doesn’t. key, default and the result are str.

On Unix, keys and values are decoded with sys.getfilesystemencoding() and 'surrogateescape' error handler. Use os.getenvb() if you would like to use a different encoding.

Availability: most flavors of Unix, Windows.