2.12 Itse1359-1270-functions

Table of contents

• Preface
  • What you have learned
  • What you will learn
  • Viewing tip
    • Figures
    • Listings
• General background information
• Discussion and sample code
• Visualizing a simple function
• 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.

What you have learned

So far under the general topic of control flow , you have learned how to construct while loops, for loops, and if statements. In addition, you have learned

• how to create nested loop structures ,
• how to add an else clause to while loops and for loops, and
• how to use the loop modifiers: continue and break .

What you will learn

This module will depart significantly from the above. In this module, you will learn the basics of defining and calling functions in Python.

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 . Syntax for a Python function definition.
• Figure 2 . Output produced by the code in Listing 1.
• Figure 3 . Visualizing the code from Listing 1.

Listings

• Listing 1 . A simple function named getRoot.

General background information

According to tutorialspoint -- Python Functions

A function is a block of organized, reusable code that is used to perform a single, related action. Functions provide better modularity for your application and a high degree of code reusing. As you already know, Python gives you many built-in functions like print(), etc. but you can also create your own functions. These functions are called user-defined functions.

Again according to tutorialspoint , the rules for defining a basic function are as follows:

• Function blocks begin with the keyword def followed by the function name and parentheses ( ( ) ).
• Any input parameters or arguments should be placed within these parentheses. You can also define parameters inside these parentheses.
• The first statement of a function can be an optional statement - the documentation string of the function or docstring .
• The code block within every function starts with a colon (:) and is indented.
• The statement return [expression] exits a function, optionally passing back an expression to the caller. A return statement with no arguments is the same as return None.

The docstring mentioned above is a string literal. We will ignore the docstring in this module. We will learn about tools in a future module that use docstrings to automatically produce online or printed documentation.