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!

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How to Check if a String Contains a Substring in Python

Getting Started:

Creating Main Function

Output:

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