The more I code in Python, the more I love it (my other favorite, Ruby, falls short in many critical areas that Python excels at, such as scientific computing, artificial intelligence prototyping, GPU programming extensions, etc.). The fact that I can use my C libraries for bit-level tweaking and major speedup on resource intensive tasks make Python an even bigger winner compared to many other scripting languages.
This reference book is helpful to jot your memory as you code, and although it's not by any means comprehensive, it does come very handy when you forget what regex format to use, or what binascii methods to call, etc.
The book itself is physically small and very portable.