eryksun, now I understand this is a bit more challenging because tkinter is the underlying library doing this and it is shared by other apps.

Though I still don't feel that just because its been like this since 1995 means it should stay this way. This is something which breaks other code following the python os.path.expanduser way(and probably other thing looking at the evitonmeny HOME). Not all people will try getting to the bottom of why, esspecially if they are a new user. It should just work.

Would iy be possible for tkinter to allow the user/app to decide the behavior?

Ie. Have a setting(s)/switch which allows the default behavior of setting and using HOME to be overiden.

By doing that existing apps remain unchanged and apps like IDLE could change this behavior to whatever they want when they are ready.

I think os.path.expanduser() behavior is by far more logical. Preference USERPROFILE if HOME is missing. USERPROFILE on windows is needed to even login. HOMEDRIVE/HOMEPATH is not.