idle is not opening

You will need the following PATH in your Zsh startup file (~/.zshrc) so that all of the Python 3.9 binaries can be found when you attempt to run them:

export PATH="/Library/Frameworks/Python.framework/Versions/3.9/bin:.:/usr/local/bin:${PATH}"



The Python.org installer does not do this for you, except in the Bash ~/.bash_profile dot file. Then either quit the Terminal or issue the following command in it to set the PATH update:

source ~/.zshrc

One of the solutions mentioned at that dialog's Python.org link is to name your python script with a name that does not collide with a known Python library name (e.g. subprocess.py, tkinter.py, random.py, etc.). If you are running any anti-virus software, remove it as it may be interfering with idle.

That makes sense, but also click the section above it: Accesso Completo al disco, and make sure that it is also checked there.

It could be something else entirely; anyway, to add an application to the list of Full Disk Access just click the + button and select it.

If this doesn’t help, please run Etrecheck and post its full report here, so we can look for possible issues. Can you think of any recent changes, like new installation of software, which could have had an impact?

Click Share Report->Copy; then start a new reply here, click the "additional text" button and paste.

The box you mentioned in System Preferences, is it the “Full Disk Access”?

By default, you will not have a /Users/username/.zshrc file in your home directory. Using a plain text editor (e.g. BBEdit), create a new .zshrc file, and copy/paste that PATH statement into it, and save it. Every time that you launch the Terminal, Zsh will read that file and set your PATH so you can use Python and Idle without further PATH-related issues.