While loop for a raw_input gives strange output in Python

Question

No mather what input I give I get the output "I think you're to old to go on an adventure. Your adventure ends here." Like if I input 17 I get "I think you're to old to go on an adventure. Your adventure ends here." and if I input 18-59 I get "I think you're to old to go on an adventure. Your adventure ends here."

while True:
    age = raw_input("\n So tell me " + str(name) + ", how old are you?: ")
    if age.isdigit() == False:
        print "\n Please, put only in numbers!"
        time.sleep(3)
    elif age < 18:
        print "\n %s. A minor. You got to be atleast 18 to go on this adventure. Your adventure ends here." % age
        time.sleep(7)
        exit(0) 
    elif age >= 60:
        print "\n %s. I think you're to old to go on an adventure. Your adventure ends here." % age
        time.sleep(5)
        exit(0)
    else:
        print "\n %s. You're starting to get old." % age
        break

raw_input gives you a string, every time, so you can't compare it to numbers. Try int(raw_input(...)). — TheSoundDefense
– TheSoundDefense, Commented Aug 23, 2014 at 0:38

abarnert · Accepted Answer · 2014-08-23 00:44:03Z

3

You need to compare your input as an int

age = int(raw_input("\n So tell me " + str(name) + ", how old are you?: "))

Otherwise you are comparing a str to an int. See the following example

>>> 5 < 10
True
>>> type(5)
<type 'int'>

>>> '5' < 10
False
>>> type('5')
<type 'str'>

In Python 2.x, comparing values of different types generally ignores the values and compares the types instead. Because str >= int, any string is >= any integer. In Python 3.x you get a TypeError instead of silently doing something confusing and hard to debug.

edited Aug 23, 2014 at 0:44

abarnert

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answered Aug 23, 2014 at 0:38

Cory Kramer

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6 Comments

abarnert Over a year ago

One problem: he's checking age.isdigit, so this is too early to convert it to int. You either need to move the conversion into an else clause under that first if, or use a try/except instead of an if, or otherwise restructure things in some way.

Markus Rexhepi-Lindberg Over a year ago

That gives me a 'int' object has no attribute 'isdigit' Is it because 'isdigit' only works with strings?

Cory Kramer Over a year ago

Correct. If you try to cast a str to an int that contains letters, for example, you will get a ValueError. So you could check for digits first before trying to cast.

TheSoundDefense Over a year ago

In that case, try testing on elif int(age) < 18 and elif int(age) >= 60.

Markus Rexhepi-Lindberg Over a year ago

That still gives me 'int' object has no attribute 'isdigit'

|

TheSoundDefense · Accepted Answer · 2014-08-23 01:08:35Z

The problem is that raw_input always returns a string object, and those don't really compare to int types. You need to do some type conversion.

If you want to use isdigit to test if the input is a number, then you should proceed this way:

while True:
    age = raw_input("\n So tell me " + str(name) + ", how old are you?: ")
    if age.isdigit() == False:
        print "\n Please, put only in numbers!"
        time.sleep(3)
    elif int(age) < 18:
        print "\n %s. A minor. You got to be atleast 18 to go on this adventure. Your adventure ends here." % age
        time.sleep(7)
        exit(0) 
    elif int(age) >= 60:
        print "\n %s. I think you're to old to go on an adventure. Your adventure ends here." % age
        time.sleep(5)
        exit(0)
    else:
        print "\n %s. You're starting to get old." % age
        break

However, you can simplify the code a little by converting to an integer right away, and just catching the exception if it's an invalid string:

while True:
    try:
        age = int(raw_input("\n So tell me " + str(name) + ", how old are you?: "))
        if age < 18:
            print "\n %s. A minor. You got to be atleast 18 to go on this adventure. Your adventure ends here." % age
            time.sleep(7)
            exit(0) 
        elif age >= 60:
            print "\n %s. I think you're to old to go on an adventure. Your adventure ends here." % age
            time.sleep(5)
            exit(0)
        else:
            print "\n %s. You're starting to get old." % age
            break
    except ValueError:
        print "\n Please, put only in numbers!"
        time.sleep(3)

Thanks, worked perfect with the try and except exceptions.

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