Kang Zhang has been busy on a Google Summer of Code project to create a cross platform keychain library for Python.
The Python keyring lib provides a easy way to access the system keyring service from python. It can be used in any application that needs safe password storage. It supports OSX, KDE, Gnome and Windows's native password storing services. Besides this, it is shipped with kinds of Python implemented keyring for the left environments.
It's also been written in a way that makes it possible to create your own Keyring backend if you want to.
As this provides a native Python interface to the OSX keychain I'd certainly recommend looking at this over and above my own noddy OSX keychain wrapper.
See the site for more info: http://home.python-keyring.org