Use try catch statement for empty input

Question

I was attempting to distinguish an empty input from others using the try catch statement. Currently, I have this.

while True:
    try:
        user = int(input("Please enter an integer"))
        break
    except ValueError:
        print("Must be an integer")

The problem comes from the fact that I would like a separate error statement if the user does not enter anything and only presses the enter key. However, it still reads that particular input as a ValueError and gives the me the message above no matter what else I try.

You could just check the input before passing to int. If you want a one-liner, you could also do: int(input("Please enter an integer") + 1/0). That will raise ZeroDivisionError if empty string. — swstephe
– swstephe, Commented Oct 26, 2014 at 16:57
I'm sorry. I'm a little new to this. How would I check the input before I pass it to int? — user3495234
– user3495234, Commented Oct 26, 2014 at 17:04
value = input("Please enter an integer"); if value: user = int(value) — swstephe
– swstephe, Commented Oct 30, 2014 at 2:23

Community · Accepted Answer · 2017-05-23 12:11:42Z

1

You can test if the string is not empty.

while True:
    try:
        s = input("Please enter an integer")
        if not s:
             print ("Input must not be empty")
        elif not s.isdigit():
             print ("Input must be a digit")
        else:
            user = int(s)
            break
    except ValueError:
        print("Must be an integer")

edited May 23, 2017 at 12:11

CommunityBot

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answered Oct 26, 2014 at 17:18

CHW

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2 Comments

user3495234 Over a year ago

Thank you. It looks like that works. Though if you don't mind, I had a related question. What if you wanted the user to enter a string such as a letter and have the program return an error if the user entered an integer?

CHW Over a year ago

Have a look at this question: stackoverflow.com/questions/21388541/… I updated my answer. If this answers your question, please mark my answer as accepted.

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