Python Check if String is Integer

In this article, we will write a program in python that will check if a string is an integer or not.

We will create a function that will take a string as input and returns a Boolean value (true or false) based on the condition if it is an integer or not. We will take the input from the user and call the function. After storing the result, we will print on the console whether the string is an integer or not.

If all the characters of an inputted string are between ‘0’ and ‘9’, then it means that the string is an integer.

For Example:

123, It is an Integer because all the characters are between 0 and 9.

35446554667876832, It is also an Integer because all the characters are between 0 and 9 only.

234t5, It is not an Integer because it contains a character ‘t’ which is not between 0 and 9.

If any character is not following the rule, then we can consider that the string is not an Integer.

# Function to check if a string is Integer of Not
def checkInteger(str1):
    """
    Function to returns if a string is Integer or Not
    Input : String value
    Output : Boolean Value ( True or False )
    """
    length = len(str1) # Find the length of the string
    # loop from 0 to length - 1 
    for i in range(0, length):
        # if the character is not greater than 0 and less than 9
        # it means that the string contains any alphabetic character
        # so it is not an integer. In this case return False
        # otherwise return True after checking all the characters
        if (not (str1[i] >= '0' and str1[i] <= '9')):
            return False

    return True

# Take string as input from the user
str1 = input("Enter a String : ")

# Call the function and store the result
result = checkInteger(str1)

# If result is True then print that it is an integer
# Else print that it is not an Integer
if (result):
    print(f"{str1} is an Integer")
else:
    print(f"{str1} is not an Integer")

Testcase 1: When the input is 123.

Output:

PS C : \ Users \ ASUS \ Desktop \ Crazy Programmer Work > python -u " c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py "
Enter a String : 123
123 is an Integer

Testcase 2: When the input is 236r.

Output:

PS C : \ Users \ ASUS \ Desktop \ Crazy Programmer Work > python -u " c : \ Users \ ASUS \ Desktop \ Crazy Programmer Work \ test.py "
Enter a String : 236r
236r is not an Integer

If all the characters of a string are between 0 and 9 then we can say that the string is an integer otherwise it is not considered an integer. We have seen the program for the same where we created a function that takes a string as input and tells us if the string is an integer or not.