IDLE is the Integrated DeveLopment Environment for Python

FEATURES

IDLE has the following features:

- coded in 100% pure Python, using the Tkinter GUI toolkit (i.e. Tcl/Tk)

- cross-platform: works on Windows and Unix (on the Mac, there are
currently problems with Tcl/Tk)

- multi-window text editor with multiple undo, Python colorizing
and many other features, e.g. smart indent and call tips

- Python shell window (a.k.a. interactive interpreter)

- debugger (not complete, but you can set breakpoints, view  and step)