IPython, which is available at http://ipython.org/, is a free, open source project available for Linux, Unix, Mac OS X, and Windows. The IPython authors only request that you cite IPython in any scientific work where IPython was used. IPython provides an architecture for interactive computing. The most notable part of this project is the IPython shell. IPython provides the following components, among others:
Interactive Python shells (terminal-based and Qt application)
A web notebook (available in IPython 0.12 and later) with support for rich media and plotting
IPython is compatible with Python versions 2.5, 2.6, 2.7, 3.1, 3.2, 3.3, and 3.4. The compatibility depends on the IPython version. For instance, IPython 2.3.0 requires Python 2.7 or 3.3+.
You can try IPython in the cloud without installing it on your system by going to http://www.pythonanywhere.com/try-ipython/. There is a slight delay compared to locally installed software, so this is not as good as the real thing. However, most of the features available in the IPython interactive shell seem to be available. PythonAnywhere also has a Vi (m) editor, which if you like vi, is obviously great. You can save and edit files from your IPython sessions.