Comparing numbers give the wrong result in Python

问题:

sorry if this is a terrible question, but I am really new to programming. I am attempting a short little test program.

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.') 

回答1:

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.

回答2:

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: 

回答3:

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

回答4:

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.') 

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