To get the homedir in python, you can use os.path.expanduser('~').
This also works if it’s part of a longer path, such as os.path.expanduser('~/some/directory/file.txt'). If there is no ~ in the path, the function will return the path unchanged.
So depending on what you want to do it’s better than reading os.environ['HOME']
The username is available through getpass.getuser()