1.33 Itse1359-1120-empty and single-item tuples  (Page 12/2)

Table of contents

• Preface
  • Viewing tip
    • Figures
    • Listings
• Introduction
• What is a tuple?
• Sample program
  • Empty, single-item, and nested tuples
  • An empty tuple
  • A tuple with only one element
  • Nested tuples
  • Doubly-nested tuples
• Complete program listing
• Visualization of the tuples
• Run the program
• Miscellaneous

Preface

This module is one in a collection of modules on Python designed for teaching ITSE 1359 Introduction to Scripting Languages: Python at Austin Community College in Austin, TX.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view theFigures and the Listings while you are reading about them.

(Note to blind and visually impaired students: Most of the Figures and all of the Listings in this module are presented in plain text format and should be accessible using anaudio screen reader or a braille display.)

Figures

• Figure 1 . Output from the code in Listing 1.
• Figure 2 . Output from the code in Listing 2.
• Figure 3 . Output from the code in Listing 3.
• Figure 4 . Consolidated output from the program in Listing 4.
• Figure 5 . Visualization of the tuples.

Listings

• Listing 1 . Beginning of the program.
• Listing 2 . A tuple with only one element.
• Listing 3 . Create and print nested tuples.
• Listing 4 . Create and print nested tuples.

Introduction

This module is part of a series of modules designed to teach you about tuples in Python.

Previous modules have illustrated

• How to create a tuple.
• How to access a tuple item using indexing.
• How to slice a tuple.
• How to nest tuples.

This module will teach you how to create empty tuples and tuples containing only one item.

What is a tuple ?

A tuple is like a list whose values cannot be modified. It is an ordered list of objects, and it can contain references to any type of object.

• Tuples are normally written as a sequence of items contained in (optional) matching parentheses.
• A tuple is an immutable sequence.
• Items in a tuple are accessed using a numeric index.
• Tuples can be nested.

Sample Program

Empty, single-item, and nested tuples

Listing 4 shows a Python program that

• Creates an empty tuple.
• Creates a single-item tuple.
• Nests the two tuples along with some strings in a third tuple.
• Determines the length of each of the tuples.
• Displays all of the above

A consolidated output from the program is shown in Figure 4 .

A visualization of the tuples in the program is provided in Figure 5 .

An empty tuple

I will explain this program in fragments. The beginning of the program is shown in Listing 1 .

As you might have guessed from the name, an empty tuple is just a pair of empty parentheses as shown by the second statement in Listing 1 . (The parentheses aren't optional for an empty tuple.)