Wing IDE is a powerful commercial development environment for the Python programming language.

Wing provides auto-completion, call tips, integrated unit testing, a source browser, support for debugging under Zope/Plone, Django, Turbogears, CGIs, wxPython, Tkinter, PyGTK, and most other Python code,
emacs and VI/VIM key bindings, and much more.  It runs on Windows, Linux, and Mac OS X (as an X11 app on the Mac).  Wing IDE Professional licenses allow access to the product source code, and free licenses are made available for non-commercial open source developers.

More info is available at http://wingware.com/