I recommend "The Quick Python Book" by Harms and McDonald. Its strength is its brevity and *readability* -- you can actually just sit down and read it and enjoy it. It doesn't cover the newest features of Python or the most advanced, but that is not necessary in a beginner's book.
Once you're up to speed on Python, as a sysadmin you'll probably find "Python Network Programming" useful. It is not a beginner's book, but it is addressed to the kind of issues that you'll probably want to be using Python for. -- http://mail.python.org/mailman/listinfo/python-list
