How to Check if a String Contains a Substring in Python

Submitted by razormist on Monday, March 24, 2025 - 23:27.

In this tutorial, we’ll learn how to program "How to Check if a String Contains a Substring in Python." The objective is to efficiently check whether a string contains a specific substring. This tutorial will guide you through the process step by step to detect if a substring exists within a string. So, let’s get started!

This topic is straightforward to understand. Just follow the instructions I provide, and you’ll complete it with ease. The program I’ll demonstrate will show you the correct and efficient way to check whether a substring exists within a string. So, let’s dive into the coding process!

Getting Started:

First you will have to download & install the Python IDLE's, here's the link for the Integrated Development And Learning Environment for Python https://www.python.org/downloads/.

Creating Main Function

This is the main function of the application. The following code will display a simple GUI in terminal console that will display program. To do this, simply copy and paste these blocks of code into the IDLE text editor.

def check(string, sub_str):
    if (string.find(sub_str) == -1):
        print("Substring is not present")
    else:
        print("Substring is present")
 
 
while True:
    print("\n============= Check if a String Contains a Substring =============\n")
        
    string = "I love sourcecodester"
    print(string)
    sub_str = input("Enter a string: ")
    check(string, sub_str)
 
    opt = input("\nDo you want to try again?(yes/no): ")
       
    if opt.lower() == 'yes':
        ret=False
    elif opt.lower() == 'no':
        ret=True
        print("Exiting program....")
    else:
        print("Please enter yes/no:")
        break
 
    if ret == False:
        continue

This program checks if a given substring is present within the string "I love sourcecodester" using Python's find() method and repeatedly prompts the user to try again until they decide to exit.

Output:

There you have it we successfully created How to Check if a String Contains a Substring in Python. I hope that this simple tutorial help you to what you are looking for. For more updates and tutorials just kindly visit this site. Enjoy Coding!

More Tutorials for Python Language

Python Tutorials