There is no answer key for the exercises in this book. There is also no answer key if auditing the course at coursera. The only way to get the answers or grading is through the fully-paid version at coursera. There are deliberate trick questions that the text does not address, almost forcing a student to buy the paid version. For example, chapter 2 exercises require certain input() and float() expressions that the text does not address. Spent about two hours finally getting it, but only with internet searches. I paid $10 for the printed book instead of the free e-book, and one would think the $10 book would at least provide an answer key. In summary, this is a deliberate attempt to confuse a student and nearly force him or her to upgrade to the paid version in order to get the correct answers to the exercises.