Well, it's useful for people who don't know how to program and want to learn Python to program for Bioinformatics tasks. But, seriously, there is no reason why a newbie programmer should be reimplementing things BioPython does for scratch except for a learning exercise, and even then they should move on and start using BioPython's implementation unless it doesn't fit their needs. I think the book could have been better by making exercises that included BioPython. Because who needs to implement parsing the gazillion formats for the millionth time?