Learning Python 4th ed, Mark Lutz, O’Reilly, 2009
Programmers will want to read this, whether they are new to Python or have been using it for a year. It covers version 2.6 and 3.1, explaining the improvements and incompatibilities. At 1100 pages, it is huge (the 1st ed. was only 350 pages). Legendary O’Reilly quality.