In this article, we will learn to detect if the user input is empty or not in python.

In Python, we can take user input using the input function. The input function returns the user input data as a string.

To detect if the user input is an empty string, we can use the if statement to compare the user input with an empty string, eg user_input == ''.

Check if user input is empty using if statement

Here, we will use the if statement and compare the user input value to an empty string.

Example:

user_input = input('Enter your name: ')

if user_input == '':
    print('The input is Empty')

Output:

Enter your name: 
The input is Empty

Since the input() function returns a string, we can use the equality operator (==) to compare the input with an empty string.

If the if condition returns True, it will print out “The input is Empty” in the terminal.

However, if we just enter a space or whitespace, it will not be considered empty because even though it looks empty, it is a non-zero length character.

So to fix it, we use the strip method to remove all the leading and trailing whitespaces from the input value and then compare it with an empty string.

user_input = input('Enter your name: ')

if user_input.strip() == '':
    print('The input is Empty')

Now, if we want to prevent a user to enter an empty string we can use the while loop.

Prevent user from entering empty string using while loop

A while loop executes a set of statements as long as the condition is True. So we can prompt the user to input their name until they enter a non-empty string.

Example:

while True:
    user_input = input('Enter your name: ')

    if user_input.strip() != '':
        print(f'Thanks {user_input} ')
        break

The above code will keep on prompting the user to enter the name until they enter their name.

Output:

And once the user inputs a valid string the break statement will execute and it will break out (exit) of the while loop.

Check if user input is empty using the not operator

The not is a logical operator in python, which returns True if the statement is false and False if the statement is true. It just reverses the boolean of the statement.

Using this operator with the if else statement we can detect if the user input is empty or not.

Example:

user_input = input('Enter your name: ')

if not user_input.strip():
    print('The input is Empty')
else:
    print(f'thanks {user_input}')

Output:

#empty string
Enter your name:  
The input is Empty

#non-empty string
Enter your name: Jack
thanks Jack

Here, when the user enters an empty string the first block turn True and we get “The input is empty ” in our terminal. And if the input is non-empty, the else statement is executed.

Conclusion: Here, we have learned to check for empty user input using if statement, while loop, and the not operator. Depending on our program we can use any of the above-mentioned methods.