-1

I'm trying to validate that a user input int is numbers only. This has been my most recent try:

while True:

    NumCars = int(input("Enter the number of cars on the policy: "))
    NumCarsStr = str(NumCars)
    if NumCarsStr == "":
        print("Number of cars cannot be blank. Please re-enter.")
    elif NumCarsStr.isalpha == True:
        print("Number of cars must be numbers only. Please re-enter.")
    else:
        break

With this, I get the following error:

line 91, in <module>
    NumCars = int(input("Enter the number of cars on the policy: "))
ValueError: invalid literal for int() with base 10: 'g'

(I entered a "g" to test if it was working) Thanks in advance!

jonahpocalypse
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    Take the input as a _string_, do whatever checks you want on that, _then_ try to cast it as integer. Also `NumCarsStr.isalpha` will _never_ be `== True`. You need to _call_ the function. – Pranav Hosangadi Nov 28 '22 at 16:40
  • Does this answer your question? [Asking the user for input until they give a valid response](https://stackoverflow.com/questions/23294658/asking-the-user-for-input-until-they-give-a-valid-response) – Pranav Hosangadi Nov 28 '22 at 16:40
  • This does not solve the issue if determining if a value passed is an integer. There are many characters that are both not a-z and not integers; typically symbols. – Devin Sag Nov 28 '22 at 16:57

4 Answers4

2

Thank you everyone for your suggestions! Unfortunately none of these answers did quite what I wanted to do, but they did lead me down a thought process that DID work.

 while True:

        NumCars = (input("Enter the number of cars on the policy: "))
        if NumCars == "":
            print("Number of cars cannot be blank. Please re-enter.")
        elif NumCars.isdigit() == False:
            print("Number of cars must be numbers only. Please re-enter.")
        else:
            break

After changing the NumCars input to a string, I validated with isdigit, and then when I needed the variable for the calculations, I converted it to integers at the instances where the variable would be used for calculations.

I don't know if it was the easiest or fastest way of doing this, but it worked!

jonahpocalypse
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1

Use try / except, and then break the loop if no exception is raised, otherwise capture the exception, print an error message and let the loop iterate again

while True:
    try:
        NumCars = int(input("Enter the number of cars on the policy: "))
        break
    except ValueError:
        print("You must enter an integer number")
Sembei Norimaki
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0

if type(input) == int: do_code_if_is_numbersonly() else: print("Numbers Only")

This checks the type of the input, and if it is integer (number) it does example code, otherwise it prints Numbers Only. This is a quick fix but in my opinion it should work well.

user20624405
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-1

You can utilize the .isnumeric() function to determine if the string represents an integer.

e.g;

    NumCarsStr = str(input("Enter the number of cars on the policy: "))
    ...
    ...
    elif not NumCarsStr.isnumeric():
        print("Number of cars must be numbers only. Please re-enter.")
Devin Sag
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