It looks like the lack of completions in msg375769 is a problem with Tk 8.6.8 as used by the python.org installers.

I have a build of master with Tk 8.6.10 on my DTK system and with that Edit->Show completions works in a shell window.

However: Ctrl+s does not show the completion pop-up, even though the "Edit" button in the application menu flashes (which indicates that Ctrl+s is recognised as a keyboard shortcut).  Just using Tab for completion works fine though (shows the completion pop-up).

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I did get a similar traceback to the one in msg375764 once, this is without using multiprocessing. I haven't been able to reproduce this yet.

python3.10 -m idlelib  
Exception in Tkinter callback
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/tkinter/__init__.py", line 1884, in __call__
    return self.func(*args)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/idlelib/autocomplete_w.py", line 248, in winconfig_event
    acw_width, acw_height = acw.winfo_width(), acw.winfo_height()
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/tkinter/__init__.py", line 1290, in winfo_width
    self.tk.call('winfo', 'width', self._w))
_tkinter.TclError: bad window path name ".!listedtoplevel.!frame.text.!toplevel8"