With Python 3, IDLE.app is easily accessible from the
/Applications/Python3.7 folder.
For Python 2, you can either find the IDLE app by digging
deep into the installed Python folder, or do the following:
Start the Applescript editor by going to the magnifying glass
on the top bar and typing "script" or "applescript".
One of these should return a top hit of "Script Editor". Hit the return
key or click on the entry; this should start Script Editor".
In the Script Editor, enter the following:
do shell script "python -c 'import idlelib.idle'"
Save the file with file format of "Application"
If you save the script on your Desktop folder, a new icon
should appear on your desktop and you can just double-click it.
If you prefer not to clutter up your desktop, you can save the
script to your Documents or Application folder. You then have to
go into Finder, find the saved script and double-click on it.