if statement - Comparing numbers give the wrong result in Python

5
votes

If I enter any value less than 24, it does print the "You will be old..." statement. If I enter any value greater than 24 (ONLY up to 99), it prints the "you are old" statement.

The problem is if you enter a value of 100 or greater, it prints the "You will be old before you know it." statement.

print ('What is your name?')
myName = input ()
print ('Hello, ' + myName)
print ('How old are you?, ' + myName)
myAge = input ()
if myAge > ('24'):
     print('You are old, ' + myName)
else:
     print('You will be old before you know it.')
4
pythonif-statement
change it to int(myAge) > 24: and it should work. - Keiwan
"if you enter a value of 100 or greater" -- really? What about 263? - Robᵩ
To expand on Keiwan's comment - '24' is a string and not a number, so when you do comparisons to it, something like '100' comes before '24' because '1' comes before '2'. This is called lexicographic ordering. - wkl
Thank you, this really clears it up for me! I have no programming background, but I really want to learn. - Raspbian
Check out the excellent tutorial bellow - RFV

4 Answers

6
votes

You're testing a string value myAge against another string value '24', as opposed to integer values.

if myAge > ('24'):
     print('You are old, ' + myName)

Should be

if int(myAge) > 24:
    print('You are old, {}'.format(myName))

In Python, you can greater-than / less-than against strings, but it doesn't work how you might think. So if you want to test the value of the integer representation of the string, use int(the_string)

>>> "2" > "1"
True
>>> "02" > "1"
False
>>> int("02") > int("1")
True

You may have also noticed that I changed print('You are old, ' + myName) to print('You are old, {}'.format(myName)) -- You should become accustomed to this style of string formatting, as opposed to doing string concatenation with + -- You can read more about it in the docs. But it really doesn't have anything to do with your core problem.

1
votes

The string '100' is indeed less than the string '24', because '1' is "alphabetically" smaller than '2'. You need to compare numbers.

my_age = int(input())
if my_age > 24:
1
votes
print ('What is your name?')
myName = input ()
print ('Hello, ' + myName)
print ('How old are you?, ' + myName)
myAge = input ()
if int(myAge) > 24:
     print('You are old, ' + myName)
else:
     print('You will be old before you know it.')

Just a small thing about your code. You should convert the input from myAge to an integer (int) (number) and then compare that number to the number 24.;

Also, you should usually not add strings together as it is consider non-pythonic and it slow. Try something like print ('Hello, %s' % myName) instead of print ('Hello, ' + myName).

Python Strings Tutorial

0
votes

Use int(myAge). I always use raw_input and also, you dont have to print your questions. Instead put the question in with your raw_inputs like so:

myName = raw_input("Whats your name?")
print ('Hello, ' + myName)
myAge = raw_input('How old are you?, ' + myName)
if int(myAge) > ('24'):
    print('You are old, ' + myName)
else:
    print('You will be old before you know it.')