Found a thread on Python editors in this article. Made me think a bit about my own environment, which is Emacs with the Emacs Python Mode, which I'm happy with. But I'd be interested in an editor that supported folding, such as SciTe, Leo, or the PythonCard Editor. This Page has an extensive list and links to all editors. There's a thread here about implementing a folding mode in emacs, which is probably the way I'll have to go, since I'm too much of a mossback to change drastically.