What platform-specific GUI toolkits exist for Python?
The Mac port by Jack Jansen has a rich and ever-growing set of modules that support the native Mac toolbox calls. The port includes support for MacOS9 and MacOS X’s Carbon libraries. By installing the PyObjc Objective-C bridge, Python programs can use MacOS X’s Cocoa libraries. See the documentation that comes with the Mac port.
PythonWin by Mark Hammond includes an interface to the Microsoft Foundation Classes and a Python programming environment using it that’s written mostly in Python.