Part of the reason for Python’s popularity is the availability of many high-quality libraries that help with various software tasks. In this appendix are descriptions of a few of the most popular packages.
It is useful to keep in mind that many of these packages may work only with specific versions of Python (which you can always download for free from www.python.org). In particular, many packages do not yet support Python 3, so you may need to use Python 2.6 (or later) to run some of these. Fortunately, if you already know Python 3, it is not too hard to step back a version to use Python 2. Appendix B briefly discusses some of the major differences between Python 2 and Python 3.