This article is created to cover a program in Python that checks whether a specified substring (a character or a phrase) is present in a given string or not. This article contains two programs:

1. Check if a substring is available in a given string.
2. Check if a substring is not available in a given string.

Python to check if a substring is in a string

The question is: write a Python program to check if a substring is available in a string. The value of both strings and substrings must be received by the user at runtime of the program. The answer to this question is the program given below:

print("Enter the String: ", end="")
MyStr = input()

print("\nEnter the Substring: ", end="")
MySubStr = input()

if MySubStr in MyStr:
    print("\nYes,\nThe substring is available in the string.")
else:
    print("\nNo,\nThe substring is not available in the string.")

The snapshot given below shows a sample run of this program with user input, "Python is easy to learn" as a string and "easy" as a substring:

Note: The in operator is used to check the availability of a specified value in a specified sequence.

But the problem with the above program is that sometimes the user needs to check whether a substring is in the given string or not, with or without caring about the uppercase or lowercase characters. Therefore, we need to create a program that gives users options on how to proceed using both. For example:

print("Enter the String: ", end="")
MyStr = input()
print("Enter the Substring: ", end="")
MySubStr = input()

print("\n1. Uppercase/Lowercase matters")
print("2. Uppercase/Lowercase doesn't matters")
print("Enter Your Choice (1 or 2): ", end="")
choice = int(input())

if choice == 1:
    if MySubStr in MyStr:
        print("\nYes,\nThe substring is available in the string.")
    else:
        print("\nNo,\nThe substring is not available in the string.")

elif choice == 2:
    if MySubStr.lower() in MyStr.lower():
        print("\nYes,\nThe substring is available in the string.")
    else:
        print("\nNo,\nThe substring is not available in the string.")

else:
    print("\nInvalid Choice!")

The sample run with user input "Python is fun" as a string, "Fun" as a substring, and "2" as a choice to check the availability of a given phrase in a given string without caring about uppercase or lowercase letters is shown in the snapshot given below:

And the following snapshot shows another sample run, with the first two inputs being the same as the above sample run and the choice being "1":

Python to check if a substring is not in a string

This is the reverse of the above program. That is, this program checks whether a specified substring is not in a string or in the string. To do this task, use not before "in", that is, "not in", instead of "in". For example:

print("Enter the String: ", end="")
x = input()
print("Enter the Substring: ", end="")
y = input()

if y not in x:
    print("\n'", y, "' is not available in '", x, "'", sep="")
else:
    print("\n'", y, "' is available in '", x, "'", sep="")

Here is its sample run with user input "codescracker.com" as a string and "org" as a phrase to confirm whether it is not available in the given string or whether it is in the given string:

The second program from the previous section can also be created in a similar way in this section too. The only difference is that we need to replace "in" with "not in". That's it. Come on, do it yourself.

Python Online Test

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