Introducing Python, 2nd Edition

Chapter 7. Tuples and Lists

The human animal differs from the lesser primates in his passion for lists.

H. Allen Smith

In the previous chapters, we started with some of Python’s basic data types: booleans, integers, floats, and strings. If you think of those as atoms, the data structures in this chapter are like molecules. That is, we combine those basic types in more complex ways. You will use these every day. Much of programming consists of chopping and gluing data into specific forms, and these are your hacksaws and glue guns.

Most computer languages can represent a sequence of items indexed by their integer position: first, second, and so on down to the last. You’ve already seen Python strings, which are sequences of characters.

Python has two other sequence structures: tuples and lists. These contain zero or more elements. Unlike strings, the elements can be of different types. In fact, each element can be any Python object. This lets you create structures as deep and complex as you like.

Why does Python contain both lists and tuples? Tuples are immutable; when you assign elements (only once) to a tuple, they’re baked in the cake and can’t be changed. Lists are mutable, meaning you can insert and delete elements with great enthusiasm. I’ll show many examples of each, with an emphasis on lists.

Tuples

Let’s get one thing out of the way first. You may hear two different pronunciations for tuple. Which is right? If you guess wrong, do you risk being considered a Python