PyRAF is a Python replacement for the IRAF CL. There is a description and a tutorial at http://www.stsci.edu/resources/software_hardware/pyraf.
PyRAF is already installed as part of SSBREL, SSBX, and SSBDEV. You do not need to install anything yourself, but you do need to do some basic configuration.
In IRAF, you normally must have a login.cl file in your current directory when you start CL. PyRAF uses that same login.cl if it exists, but looks for a fallback in $HOME/iraf if it does not. It is often convienent to use the "fallback" login.cl as the primary configuration file so that you can start PyRAF from any directory.
Use "mkiraf" to create a new login.cl in $HOME/iraf: