How to Use def () Function in Python

How to Use def () Function in Python

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Vikram Singh
Assistant Manager - Content
Updated on Oct 13, 2023 14:03 IST

The def () keyword in python is used to define the function that users can use to built their own function. In this article, we will discuss how to use def () keyword to create your own function in python.


In this article, we will learn how to create our own function in Python. In Python, we can create functions using def keywords.

So, without further delay, let’s move on to learn how to use a def keyword to define a function in Python.

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Table of Content

Functions in Python

In any programming language, function plays an important role. It is a set of instructions that can be repeatedly used. In simple terms, it is a reusable piece of code to carry out a specific task. 

In Python, we mainly have three different types of functions:

  • Built-in Function
    • They are pre-defined functions that can be directly used.
    • Example: abs (), min (), max (), print (), type (), etc.
  • User Defined Function
    • They are not pre-defined functions; Python allows users to create their own functions as per their requirements.
  • Anonymous Function
    • Besides built-in and user-defined functions, Python has an anonymous function that is used without defining a name.
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How to Define and Call a Function

UserDefine Function

If you have to create a program that you are using repeatedly in your program, then you can define your functions. In Python, user can define their function using def keywords.

  • def keyword can be used to define the method of a class.
  • it is also used to define member function of a class __init__().

Now, let’s see how def keyword is used to define a function.


def function_name(arguments):
    “ “ “
    functions logics
    ” ” ” 
    return values


  • def: It is a keyword that is used to define (declare) a function.
  • function_name: It is a name that you give to your function.
    • The function name should be straightforward, easily remembered, and understandable.
  • arguments: value that is passed in the function.
    • There are two special types of arguments:
      • *args: it is used when we don’t know how many arguments a function will receive during runtime.
      • **kwargs:  It is used if we want to receive named arguments
  • return: It is an optional value that returns a value from the function.
    • Function immediately exits when they come across the return statement.
    • It can be used to return multiple values.
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Example-1: Create a function to find the cube of a number.

def cubic(n):
cube = n*n*n
return cube
# Using the cubic function find the cube of 3
result = cubic(3)
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Example-2: Create a function to find the sum of two numbers.

def addition(m, n):
add = m + n
print('Addition of two numbers is:', add)
# Find the sum of 9 and 10
addition(9, 10)
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Addition of two numbers is: 19

Example-3: Create a function using *args

def addition(*args):
add = 0
for i in args:
add += i
return add
# Find the sum of first 5 integers
print('Sum of first five integers is:', addition(1, 2, 3, 4, 5))
# Find the sum of first 3 prime numbers
print('Sum of first 3 prime numbers is:', addition(2, 3, 5))
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Sum of first five integers is: 15
Sum of first 3 prime numbers is: 10

Example – 4: Create a function using **kwargs

def roll_number(**kwargs):
for i in kwargs:
print(i, kwargs[i])
# Find the roll number and student name
roll_number(A = 1001, B = 1002, C = 1003, D = 1004, E = 1005)
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A 1001
B 1002
C 1003
D 1004
E 1005

Until now, we have a clear understanding of what is python function and how to define a function in Python. While defining a function, we use an argument to pass the value in the function. Python allows using the user-defined function as an argument.
Let’s see the below example of how we can pass a function as an argument.

Passing Function as an Argument

def cubic(n):
return n * n * n
result = list(map(cubic, [1, 2, 3]))
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About the Author
Vikram Singh
Assistant Manager - Content

Vikram has a Postgraduate degree in Applied Mathematics, with a keen interest in Data Science and Machine Learning. He has experience of 2+ years in content creation in Mathematics, Statistics, Data Science, and Mac... Read Full Bio