About the names

You may have noticed that, in order to keep the examples as short as possible, I have called many objects using simple letters, like a, b, c, d, and so on. This is perfectly OK when you debug on the console or when you show that a + b == 7, but it's bad practice when it comes to professional coding (or any type of coding, for that matter). I hope you will indulge me if I sometimes do it; the reason is to present the code in a more compact way.

In a real environment though, when you choose names for your data, you should choose them carefully and they should reflect what the data is about. So, if you have a collection of Customer objects, customers is a perfectly good name for it. Would customers_list, customers_tuple, or customers_collection work as well? Think about it for a second. Is it good to tie the name of the collection to the datatype? I don't think so, at least in most cases. So I'd say if you have an excellent reason to do so, go ahead; otherwise, don't. The reason is, once that customers_tuple starts being used in different places of your code, and you realize you actually want to use a list instead of a tuple, you're up for some fun refactoring (also known as wasted time). Names for data should be nouns, and names for functions should be verbs. Names should be as expressive as possible. Python is actually a very good example when it comes to names. Most of the time you can just guess what a function is called if you know what it does. Crazy, huh?

Chapter 2 of Meaningful Names of Clean Code, Robert C. Martin, Prentice Hall is entirely dedicated to names. It's an amazing book that helped me improve my coding style in many different ways, and is a must-read if you want to take your coding to the next level.