IPython
IPython is an alternate shell for interactively working with Python. It provides several enhancements to the default REPL provided by Python.
To start IPython, simply execute the ipython command from the command line/Terminal. When started you will see something like the following:
Likewise, output from any particular entry you make will be prefaced with Out [x]:, where x matches the number of the corresponding In [x]:. The following screenshot demonstrates this:
This numbering of in and out statements will be important to the examples as all examples will be prefaced with In [x]: and Out [x]: so that you can follow along.
Note that these numbers are purely sequential. If you are following through the code in the text and errors occur in the input or you enter additional statements, the numbering may get out of sequence (they can be reset by exiting and restarting IPython). Please use them purely as reference.