Answer: B Solution: x and y are sets. What does the `-` do on sets? It computes the "set difference". The diagram makes it clear (credit in description): The shaded region is the part of A which is not in B. That is the set difference. +

Answer: A Solution: a and b are sets. The code computes a ^ b What is this operator ^? The operator's action is called Symmetric Difference. The diagram shows it the symmetric difference of A and B as shaded: +

In Python there is a module called `decimal` which has you covered. It is designed specially for exactly representing decimal numbers. There you won't have such problems. See image for demo. I hope this answer was helpful!

You can count backwards from the rightmost item. The 2nd-last is at index -2, the 3rd-last at -3, and so on. See image: Applying to this question +

Integrating solutions

Which of the following snippets is preferable?

BONUS quick summary of how to decompose a list comp:

`extend` and `append` are both list methods that seem similar But don't confuse `extend` with `append` `append` just adds the argument as one item to the list `extend` unpacks the iterable and adds each item See image for example:

Python quiz

Which one do you choose?

Novel idea of the century! They discovered the importance human expertise