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This module will teach you about unpacking tuples in Python.

Table of contents

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 the Figuresand Listings while you are reading about them.

(Note to blind and visually impaired students: most of the Figures and all of the Listings inthis module are presented in plain text format and should be accessible using an audio 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 . Output from the code in Listing 4.
  • Figure 5 . Visualization of the tuples in the program.
  • Figure 6 . Output from the modified program.

Listings

  • Listing 1 . Beginning of the program.
  • Listing 2 . Unpack the tuple and print individual elements.
  • Listing 3 . Unpack the tuple into the mutable list.
  • Listing 4 . Complete program listing.

Introduction

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

Earlier modules have illustrated

  • How to create (pack) a tuple.
  • How to access a tuple item using indexing.
  • How to slice a tuple.
  • How to nest tuples.
  • How to create empty tuples.
  • How to create single-item tuples.

This module will teach you about unpacking tuples.

What is a tuple ?

A tuple is an immutable ordered list of objects. It can contain references to any type of object. See earlier modules in this series for a more detaileddescription.

Sample program

Program to unpack a tuple

Listing 4 presents a Python program that:

  • Creates (packs) two simple tuples.
  • Creates (packs) a third tuple by concatenating the first two tuples.
  • Displays the third tuple.
  • Unpacks the third tuple, assigning each item of the tuple into a separate variable.
  • Displays each of the variables.
  • Creates and displays a mutable list object containing five strings.
  • Unpacks the tuple created earlier assigning the four items from the tuple into the first four items in the list.
  • Displays the list.

Figure 4 shows the output produced by the program in Listing 4 .

Figure 5 shows a visualization of the tuples in the program after the first five statements in the code block have been executed.This is a case where you need to step through the program and observe changes in the diagram on the right to appreciate the behavior of the program.

I will explain this program in fragments. Listing 1 shows the beginning of the program.

Listing 1 . Beginning of the program.
# Illustrates unpacking a tuple #------------------------------# Create a pair of tuples t1 = 1,2t2 = "A","B" # Concatenate and print themt3 = t1 + t2 print(t3)

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Source:  OpenStax, Itse 1359 introduction to scripting languages: python. OpenStax CNX. Jan 22, 2016 Download for free at https://legacy.cnx.org/content/col11713/1.32
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