Learn A to Z About Python Functions

Python is one of the most popular programming languages available today. It is widely used in various business sectors, such as programming, web development, machine learning, and data science. Given its widespread use, it's not surprising that Python has surpassed Java as the top programming language. In this article, you will learn about Python functions. This article will cover the following topics:

  • What are Python functions?
  • How to create and call a function
  • What are arguments in a Python function?
    • Types of arguments
  • The return statement in Python functions
  • Nested functions
  • Recursive functions

What Are Python Functions?

A function is a set of code that performs any given task, enabling the programmer to modularize a program. All variables created in function definitions are local variables; they are known only to the function in which they are declared.

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How to Create and Call a Function

In Python, you create a function by using the def keyword. Let’s look at an example of this.

Syntax: def name(arguments):


  return value



Fig: Python function

The def keyword only creates and defines a function. To call the function, use the function name, followed by parentheses.



Fig: To call a Python function

Common rogramming error:

Failure to indent the body of a function is a syntax error.

Good programming practice:

It is not advisable to use identical names for the arguments passed to a function, and the corresponding parameters in the function definition.

What Are Arguments in a Python Function?

You can send information to a function by passing values, which are known as arguments or parameters. They are mentioned after the function name inside the parentheses. You can add as many arguments you’d like by separating them with a comma.



Fig: Function parameters

Keep in mind that the function must be called with the correct number of arguments. If your function has two arguments, it must be called with two arguments.

Common programming error:

Failure to place a colon (:) after a function’s parameter list is a syntax error.

Types of Arguments

1. Default arguments

Functions can be defined with default arguments. If the values for the arguments are not supplied when the function is called, the default argument is used.



Fig: Default arguments

2. Arbitrary arguments

Arbitrary arguments are used when you want the function to take an unlimited number of arguments. When you add an asterisk ( * ), it will receive a tuple of arguments.



Fig: Arbitrary arguments

3. Keyword arguments

You can pass the arguments in a non-positional manner using keyword arguments. Let’s look at an example to understand this:


Fig: Keyword argument

The Return Statement in Python Functions

To return a value from a function, we use a return statement. It “returns” the result to the caller.



Fig: Return statement in Python functions

A function always returns a value. If a user doesn’t include a return statement, it returns None.

Nested functions

A nested function is a function that is defined inside another function—it is also called an inner function. One of the main reasons to use nested functions is to prevent the data or functionality from being accessed by other parts of the code.



Fig: Nested functions

Recursive Function

A recursive function is a function that repeats its behavior until a specified condition is met.



Fig: Recursive function

Practice Exercises

The following hands-on exercises can give you the opportunity to test your knowledge of Python functions. 

Question 1: Write a program that calculates the squares of numbers ranging from one to 11 using a user-defined function.



Fig: Solution 1

Question 2:  Write a program that can multiply all the numbers in a list using an inbuilt function.


Fig: Solution 2

The following code executes as follows: We create a function to multiply and pass in a ‘numbers’ parameter. ‘numbers’. The for loop iterates over every element in a list and multiplies it with total until reaching the last number.

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Functions are a crucial component of any programming language. Python functions are defined using the def keyword, and we can have any number of arguments in a function. Python also supports anonymous functions. They can return a single value or yield a number of values, one by one. 

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About the Author

Aryan GuptaAryan Gupta

Aryan is a tech enthusiast who likes to stay updated about trending technologies of today. He is passionate about all things technology, a keen researcher, and writes to inspire. Aside from technology, he is an active football player and a keen enthusiast of the game.

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