Python All-in-One For Dummies, 3rd Edition

Chapter 4

Cruising Massive Data with Dictionaries

IN THIS CHAPTER

Producing a dictionary

Seeing how to loop through a dictionary

Copying dictionaries

Deleting items in a dictionary

Using multi-key dictionaries

Dictionaries, also called associative arrays in some languages, are kind of like lists, which we discuss in Chapter 3 of this minibook. But each item in the list is identified not by its position in the list but by a key. You can define the key, which is typically a string or a number. All that matters is that it is unique to each item in the dictionary.

To understand why uniqueness matters, think about phone numbers, email addresses, and Social Security numbers. If two or more people had the same phone number, whenever someone called that number, all those people would get the call. If two or more people had the same email address, all those people would get the same email messages. If two or more people had the same Social Security number, and one of those people was a million ...