Python editor/IDE for new (high school) coders?

I'm supporting a class of high school students who are new to programming, and will be learning some python. Most of these students are comfortable with computers, but not hacker types, and few if any of them have written code before.

I'm looking for an editor or an Integrated Development Environment (IDE) that won't be too scary for them, and will help them get used to the novel idea of writing code without simultaneously having to get used to the novel idea of an unfamiliar user interface.

So i can't expect them to pick up my beloved emacs, for example. But on the other end of the spectrum, i'd hate for them to try to write python in an word processor (i've seen people do it!). Here's what i think i'm looking for:

Do you have suggestions for tools that work well for the above needs? Favorites? Are there features other than the "top three" i listed above that you think i should pay attention to?

FWIW, they'll be working in a labful of machines running Ubuntu Hardy for the most part, but i'm willing to port and deploy programs (particularly ones that feel like a perfect fit) if they're not available in hardy.

Tags: ide, python, recommendations, student