CODEWITHSUNDEEP
pythonpython-3.6try-exceptvalueerror
Taavi Raudkivi
Taavi Raudkivi

Reputation: 71

How to check if user input is a string

I have two user inputs: in the first one user has to insert a text what is string type and in the second one to insert a number what is int type. I used try/except ValueError, so user couln't insert a string where int is needed. Although ValueError wouldn't work when user inserts int where string is needed.

How can input value be false, when int is inserted, where str is asked? This is my code now:

while True:
    try:
        name_input = input('Insert name')
        name = str(name_input)

        number = input('Insert number: ')
        num = int(number)

    except  ValueError:
        print('Wrong')

Upvotes: 1

Views: 14310

Answers (2)

Glenn D.J.
Glenn D.J.

Reputation: 1965

If you would like the whole name to be alphabetic you can simply add an if statement like this:

if not name.isalpha():
    print("wrong, your name can only include alphabetic characters")

Or better fitting your short example:

if not name.isalpha():
    raise ValueError

This will only accept input strings that don't contain any number at all.

If you would like to allow digits in your name as long as the name begins with a letter you could also have something like the following:

if len(name) < 1 or not name.isalnum() or not name[0].isalpha():
    raise ValueError

This checks first whether the name is at least 1 character long, then it checks whether the whole name consists solely of alphabetic characters and numbers, followed by a final check to see if the first character is an alphabetic character.

Upvotes: 3

Chris Applegate
Chris Applegate

Reputation: 762

A string with a number in it is still a valid string - it's a string representing that number as text.

If you want to check that the name is not a string composed just of digits, then the following code will work:

while True:
    try:
        name = input('Insert name: ')
        if name.isdigit():
            raise ValueError

Upvotes: 0

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