IDLE/Python

Simply the idle tool in Monterey is based on the Python 2.7.18 distribution that Apple bundles with the operating system. It launches to an entirely black panel, as does its Preference pane, so it is useless due to its dependency on a long since deprecated Tk/Tcl 8.5.9 interface library.

That leaves idle3 from the current Python 3.10.0 distribution at Python.org. That launches normally, either from the Terminal as below, or from /Applications/Python 3.10/IDLE, with the following display:

idle3 &

This version of Python is built and bundled using the Tk/Tcl 8.6.11 library and works correctly. I suggest you reboot your Mac, ensure that you have a working Internet connection, and then relaunch idle3 as I did above. See if the problem reoccurs.

Did you launch idle3 as I showed previously, or double-click it in /Applications/Python 3.10/Idle.app? Be certain that your Python3 script name is not tkinter.py, idle.py, or any library module name per Idle - Python 3.10.0 documentation.

Did you review the document that was indicated in the message window? If so, and it didn't help, I suggest contacting the IDLE developer for further assistance with this issue.

Ref: How to contact an app developer - Apple Support

Python scripts have a .py extension. Period. The IDLE application is not for opening Python scripts, or as a substitute as a Python editor. You should use it to interactively test individual lines of code, small blocks of Python code, or functions. Get a programmer's editor (e.g. BBEdit, Sublime Text 4, etc.) that understands Python and use that. Put the following as the first line in your Python3 code:

#!/usr/bin/env python3

and then from the Desktop make that Python script executable, and run it:

cd Desktop
chmod +x ./Calcolatrice.py
./Calcolatrice.py

By the way, here is how I use idle3:

Just short bursts of code to test code functionality. Now I know that it works, I can use this code in a separately edited Python script.