Introduction to Computing Using Python: An Application Development Focus

CHAPTER 2

Python Data Types

2.1 Expressions, Variables, and Assignments

2.2 Strings

2.3 Lists

2.4 Objects and Classes

2.5 Python Standard Library

2.6 Case Study: Turtle Graphics Objects

Chapter Summary

Solutions to Practice Problems

Exercises

IN THIS CHAPTER, we introduce a very small subset of Python. While small, it is broad enough to start doing interesting things right away. In the next chapters we fill in the details. We begin by using Python as a calculator that evaluates algebraic expressions. We then introduce variables as a way to “remember” results of such evaluations. Finally we show how Python works with values other than numbers: values to represent logical values true and false, text values, and lists of values.

Having seen the core types of data supported by Python, we take a step back and define precisely the concept of a data type and that of an object that stores a value of a given type. With data stored in objects, we can ignore how the data is represented and stored in the computer and work only with the abstract but familiar properties that the object's type makes explicit. This idea of abstracting important properties is a central one in computer science to which we come back several times.

In addition to the core, built-in data types, Python comes with a large library of additional types organized into modules. In this chapter's case study, we use the turtle graphics module to visually illustrate the concepts introduced in this chapter: objects, types, and ...