Python on the Mac 
Python on the Mac has the ability to work with
- Apple Events (you can use Python instead of Applescript),
- Native Mac libraries (you can call all the Objective-C libraries, including Cocoa),
- Mac application bundles ("apps", written in Python),
Python comes pre-installed on Mac OS X, but due to Apple's release cycle, it's often one or even two years old. The overwhelming recommendation of the "MacPython" community is to upgrade your Python by downloading and installing a newer version from the Python standard release page.
If you are using Mac OS X 10.5, see the Leopard wiki page for detailed information.
If you're just curious...
You don't have to download anything. You can run a Python interpreter by double-clicking on Applications / Utilities / Terminal (here's a picture), then typing "python" into the window that opens up.
You'll see a prompt that looks like this:
Python 2.3.5 (#1, Mar 20 2005, 20:38:20) [GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>>(On Mac OS X 10.3 (Panther), it will say "Python 2.3.0", an older version.)
Try typing "2 + 2" and hit "Enter":
>>> 2 + 2 4 >>>You've just evaluated your first Python expression. It's a simple environment, but good enough to work through the Python tutorial.
By the way, if you download the recommended upgrade mentioned at the top of this page, the "IDLE" development environment will make working through the tutorial a bit easier.