12 Examples To Understand Python User-Defined Functions

Everything from syntax, documentation, parameters, and arguments to local and global variables

Photo by Boitumelo Phetla on Unsplash

Hello, and welcome to my guide to Python user-defined functions. This article will cover the basics of Python user-defined functions, the syntax you must master, and examples to help you consolidate your newly acquired knowledge.

Introduction

In simple terms, a function takes an input, performs a computation, and produces an output. Python has user-defined functions, anonymous functions, and built-in functions, such as the print() function. I’m sure you will all recognise the print() function as your introductory line of code to the wonderful world of programming.

print("Hello World")
>>> Hello World

Today, however, we are going to focus on user-defined functions. In programming, you will eventually reach a point where you are regurgitating the same code over and over. This is time-consuming and unnecessarily repetitive. In programming, there is an acronym for this: DRY (don't repeat yourself)! To avoid this you can define your own functions. This will help make your code organised, manageable, and re-usable. The idea is that instead of writing the same code again and again for different inputs, you can call (use) your functions when necessary.

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The syntax is the set of rules that defines code (in this case, your function).

The first line (header)

• the keyword def
• the function name (keep it relevant — link to naming conventions)
• parentheses (), which may or may not include parameters and arguments
• and a colon :

Function/statement block (body)

• The following lines of the function block include what the function is supposed to do. All these lines have to be indented (press Tab).
• The first statement of a function can be an optional statement…