I have a list of my favorite things: my_things = ["spam","eggs","ham","cheese"] What does my_things[::-2] evaluate to?
The third argument to a Python slice is the number of steps to take when slicing. In this case, by using a negative step and default beginning and end, my_things[::-2] slices in reverse order, from the end of the list to the beginning, and skips every other item. In other words, ["cheese","eggs"].
You are building a website where people can enter the name of their favorite color and see how popular it is. Should you use a hash table to store their responses?
If your website becomes very popular, you will have difficulty accessing all this information. A hash table has extremely fast O(1) access complexity, but picking a hash table size that's large enough to fit every color is a waste of memory, and a hash table size that's too small is almost worthless. You should keep track of all the color names in an alphabetically sorted list stored in a tree. That way, you can insert new color names and check how popular other colors are in O(log n) time, no matter how many color names there are.
A friend comes to you with a question about a new startup(Yog-Ex) looking to hire her. The founder of Yog-Ex claims to have invented a revolutionary product with "the power of probiotic yogurt-derived endoplasmic reticulum". Should your friend go to work for Yog-Ex?
Your friend should not take the job. Yogurt is made with $Lactobacillus$ bacteria, and bacteria do not have any endoplasmic reticulum. Yog-Ex's founder is either mistaken or the whole company is based on lying about their core product, and either way will not be a good place to work in a year or two.