how do I launch IDLE, the development environment for Python, on Mac OS 10.7?

When you open up a new terminal window, just type in

idle

Then you will see a little rocket icon show up as IDLE loads

Then the Python shell opens up for you to edit

One way to run IDLE from spotlight or an icon in the Applications folder is to build a quick Automation for it. As mentioned by other commentators, this probably isn't necessary for Python 3, as it creates a shortcut automatically, and some hand-installed versions have tools to do this automatically. But if you want to roll your own:

1. You'll need to know the terminal command to open your version of IDLE. On my Mac right now (early 2016), running python 2.7.10, it is "idle2.7"
2. Using spotlight, or in the Utilities folder, open "Automator"
3. Choose an "Application" type document.
4. Make sure "Actions" is selected in the gray bar, upper left.
5. In the actions column, find "Run Shell Script" and double-click it, or drag it to the workflow area on the right.
6. Enter the terminal command in the parameters box that appears.
7. Save your automation (I called mine "IDLE" and put it in the Applications folder, to make it easy).
8. It's now available (as soon as spotlight indexes it) via all the normal methods. The only side-effect will be that while it's running, your menu bar will have a spinning gear over in the tray area next to the clock. This indicates an automation workflow is running. Once you close IDLE, it will go away.

In the stock Mac OS X python installation, idle is found in /usr/bin, which is not (easily) accessible from Finder and not indexed by Spotlight. The quickest option is to open the Terminal utility and type 'idle' at the prompt. For a more Mac-like way of opening it, you'll have to create a small app or shortcut to launch /usr/bin/idle for you (an exercise left to the reader).