Python input validation for both integer and string

Question

I'm new in programming and I have an issue when doing the input validation. My program requires to input number from 1 to 10 or the letter y but it seems that I cannot do an error handler for this.

def checkingInput():
    while True:
        try:
            a = input()
            if 10 >= a >= 1 or a == 'y':
                return value
            else:
                print('Invalid input!')
        except NameError:
            print('Name error!Please try again!')
        except SyntaxError:
            print('Syntax Error!Please try again!')

I presume you are using python 3 due to the print() but could you please confirm that? — jamylak
– jamylak, Commented May 10, 2012 at 5:19
SyntaxError is not an exception that normally happens at runtime. — Ignacio Vazquez-Abrams
– Ignacio Vazquez-Abrams, Commented May 10, 2012 at 5:31
I think you want ValueError instead of SyntaxError. Also you can't compare ints with strings so you should change your line to if a == 'y' or 1 <= int(a) <= 10 — jamylak
– jamylak, Commented May 10, 2012 at 5:32
Also, if this is python 3 you do not need to catch NameError either — Antti Haapala
– Antti Haapala, Commented May 10, 2012 at 5:34

Katriel · Accepted Answer · 2012-05-10 07:28:27Z

4

as jamylak suggested change the if condition to :

if a == 'y' or 1 <= int(a) <= 10:

program:

def checkingInput():
    while True:
        try:
            a = input('enter')
            if a == 'y' or 1 <= int(a) <= 10:
                return a
            else:
                print('Invalid input!')
        except ValueError:
            print('Value error! Please try again!')

edited May 10, 2012 at 7:28

Katriel

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answered May 10, 2012 at 5:35

Ashwini Chaudhary

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5 Comments

jamylak Over a year ago

doesn't work if a is 'y' since if statement checks conditions from left to right and won't be able to convert 'y' to int. Do this instead: if a == 'y' or 1 <= int(a) <= 10

Ashwini Chaudhary Over a year ago

@jamylak Thanks, I really didn't knew that If uses left to right checking.

jamylak Over a year ago

+1 Also i can't tell if that is sarcasm or not... If it is I'm sorry but I just thought it was worth explaining for other people reading this.

Ashwini Chaudhary Over a year ago

@jamylak no that isn't sarcasm, it was helpful.

Karl Knechtel Over a year ago

As an aside: proper style dictates a name of check_input - the punctuation (all lowercase with an underscore in between) is the preference of the Python community, but all programmers would prefer the name check over checking: since the function does something, give it a name that's imperative, rather than descriptive.

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