This interactive interpreter contains small upgrades to the default python interpreter.   Among others, native tab completion and a more bash like referencing of history commands.

Install on OSX 10.5 with two simple commands:

[brent@ronin ~]501$ sudo easy_install ipython
… snip….
[brent@ronin ~]502$ sudo easy_install -f http://ipython.scipy.org/dist/ readline

Enjoy!