IPython is a multiplatform, Free Software project (BSD licensed) that offers:

* An enhanced Python shell designed for efficient interactive work. It includes
  many enhancements over the default Python shell, including the ability for
  controlling interactively all major GUI toolkits in a non-blocking manner.
* A library to build customized interactive environments using Python as the
  basic language (but with the possibility of having extended or alternate
  syntaxes).
* A system for interactive distributed and parallel computing (this is part of
  IPython's new development).