2.14 Itse1359-1280-function arguments

Table of contents

• Preface
  • What you have learned
  • What you will learn
  • Viewing tip
    • Figures
    • Listings
• General background information
• Discussion and sample code
  • Passing by value or reference
    • The function definition
    • A non-technical explanation
    • Visualization of the code in Listing 1
    • A modified approach to the same objective
  • Required arguments
  • Default arguments
  • Keyword arguments
  • Variable-length arguments
    • Visualization of variable-length arguments
• Run the programs
• 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.

What you have learned

You learned the basics of defining and calling Python functions in the earlier module titled Itse1359-1270-Functions .

What you will learn

In this module, you will learn how to tap into some of the more-powerful capabilities of functions involving optional ways to use arguments. This willinclude an explanation of

• required arguments,
• default arguments,
• keyword arguments, and
• variable-length arguments.

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 the 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. Note however that the requiredindentation may not be properly represented by an audio screen reader.)

Figures

• Figure 1 . Output from the code in Listing 1.
• Figure 2 . Visualization of the code in Listing 1.
• Figure 3 . Output from the code in Listing 2.
• Figure 4 . Output produced by the code in Listing 3.
• Figure 5 . Output produced by the code in Listing 4.
• Figure 6 . Output produced by the code in Listing 5.
• Figure 7 . Visualization of variable-length arguments.

Listings

• Listing 1 . A list-modifier function.
• Listing 2 . Another list-modifier function.
• Listing 3 . Illustration of default arguments.
• Listing 4 . Illustration of keyword arguments.
• Listing 5 . Illustration of variable-length arguments.

General background information

The overall topic of function arguments in Python is broad and relatively complex. A complete treatment of the topic is beyond the scope of this collection of modules.Instead, I will provide some examples of what is possible. For a more compete treatment, I will refer you to The Python Tutorial -- More on Defining Functions and tutorialspoint -- Python Functions .

One of the fundamental concepts in computer programming is whether function parameters are passed by value or by reference . If a parameter is passed by value, the function receives a copy of the thing referred to by theparameter. Modifying that thing in the function will not modify the original.