Eryk Sun added the comment: ntpath.expanduser() no longer uses HOME (though the doc string still refers to $HOME), so at least that problem is resolved. I suppose IDLE could work around the HOME issue in Windows by passing env=os.environ.copy() in the subprocess.Popen() call that creates the subprocess. os.environ will not contain the HOME value that TCL sets in the underlying process environment. ---------- versions: +Python 3.10, Python 3.8, Python 3.9 -Python 2.7, Python 3.5, Python 3.6 _______________________________________ Python tracker https://bugs.python.org/issue27263 _______________________________________