Hide input cells #32. That would make the ability to mix hidden python stuff with purposefully displayed python. I struggled with this, too. My first attempt was for a talk at EuroPython 2014 (Brainwaves for Hackers) where I hacked the live_reveal extension to interpret skip (from the slideshow-toolbar) as hide input.
An ISO file is a complete copy of a CD or DVD. You can create ISO images yourself or download them from the Internet. For example, Linux distributions offer freely downloadable ISO files that you can burn to disc. You can use an ISO image in a variety of ways. The ISO file itself is a backup of a disc, so you can use the ISO file if you ever lose or damage the original disc CDs Are Not Forever: The Truth About CD/DVD Longevity, Mold & Rot .
ISO Recorder is a tool (power toy) for Windows XP, 2003 and now Windows Vista, that allows (depending on the Windows version) to burn CD and DVD images (DVD support is only available on Windows Vista), copy disks, make images of the existing data CDs and DVDs and create ISO images from a content of a disk folder.