Python Forum

Hello, I am new to Python and I've been playing around with the 'Hello World' script that everyone probably starts with

I wanted to see if i could you 'if' properly so I made 2 'if' lines that would print a different response depending on 'age=input()'

I created a simple equation to write if the age=input() was <'18'. It simple finds the different between 'age=input()' and '18' to print how long is left until 18.

The trouble is, if 'age=input()' is a single digit int such as 4 or 9, the script will print the line for 'age>='18'. Almost like a single digit int is greater than '18'

Here is the code:

print('hello world!')
print('What is your name?')
name=input()
print('That is a nice name, '+name)
print('How old are you, '+name+' p.s. put a zero infront of a single digit')
age=input()
if age>='18':
print("if you're "+age+", that means it's beer o'clock!")
diff=str(18-(int(age)))
if age<'18':
print('That means you have to wait '+diff+' years to have a drink on me!')

Here is the output if age is a single digit int:

hello world!
What is your name?
G
That is a nice name, G
How old are you, G p.s. put a zero infront of a single digit
2
if you're 2, that means it's beer o'clock!

Whereas is you put a '0' infront of the single digit int, it works:

hello world!
What is your name?
G
That is a nice name, G
How old are you, G p.s. put a zero infront of a single digit
02
That means you have to wait 16 years to have a drink on me!

Any help is appreciated!

See below, i used to typecast to str only at print, rest comparisons in int.

print('hello world!')
print('What is your name?')
name=input()
print('That is a nice name, '+name)
print('How old are you, '+name+' p.s. put a zero infront of a single digit')
age=int(input())
diff=18-age

if age>=18:
    print("if you're "+str(age)+", that means it's beer o'clock!")
if age<18:
    print('That means you have to wait '+str(diff)+' years to have a drink on me!')

Output:
C:\Users\sandeep\Downloads>py hh
hello world!
What is your name?
user1
That is a nice name, user1
How old are you, user1 p.s. put a zero infront of a single digit
2
That means you have to wait 16 years to have a drink on me!

C:\Users\sandeep\Downloads>py hh
hello world!
What is your name?
user2
That is a nice name, user2
How old are you, user2 p.s. put a zero infront of a single digit
0
That means you have to wait 18 years to have a drink on me!

C:\Users\sandeep\Downloads>py hh
hello world!
What is your name?
user3
That is a nice name, user3
How old are you, user3 p.s. put a zero infront of a single digit
25
if you're 25, that means it's beer o'clock!

Best Regards,
Sandeep.

GANGA SANDEEP KUMAR

Ahh legend thank you!

I tried playing around with str(int(age)) stuff like that but obviously didnt work.

Thanks for the help

Comparing strings doesn't work like comparing numbers.

String comparison is based on character code points and can be desribed as follows:

- comparing the n-th characters of each string (starting with 0-th index) using the == operator
- if they’re equal, repeat this step with the next character
- in case of two unequal characters, string with the character that has the lower code point is 'less' than other
- if all characters are equal, the strings are equal
- if one string is shorter i.e. runs out of characters during comparison (one string is a “prefix” of the other), the shorter string is “less than” the longer one

Codepoints for characters 0..9 are:

>>> [ord(str(i)) for i in range(10)]
[48, 49, 50, 51, 52, 53, 54, 55, 56, 57]

Therefore:

>>> '18' < '2'   # code point of '1' is smaller than of '2'
True
>>> '18' < '02'          # codepoint of '1' is larger than of '0'
False

Please use the

[python][/python]

tags to wrap your code. Otherwise the indentation is lost and syntax highlighting does not work.

print("hello world!")
print("What is your name?")
name = input()

print("That is a nice name, " + name)
print("How old are you, " + name + " p.s. put a zero infront of a single digit")
age = input()

if age >= "18":
    print("if you're " + age + ", that means it's beer o'clock!")
diff = str(18 - (int(age)))
if age < "18":
    print("That means you have to wait " + diff + " years to have a drink on me!")

In Line 9 you're comparing two strings.
The comparison of str is made via lexicographical order.

Here are some hexadecimal values:
Whitespace == 0x20
0 - 9 == 0x30 - 0x39
A - Z == 0x41 - 0x5a
a - z == 0x61 - 0x7a

If you compare this:
"1" > "18"

The interpreter compares char by char.

(0x31,) > (0x31, 0x38)

But if you compare "4" > "18", you have this values:

(0x34,) > (0x31, 0x38)

So, the first one is bigger and this explains why "4" > "18" == True.

If you want to compare numbers, then convert the str into int.

print("hello world!")
print("What is your name?")
name = input()

print("That is a nice name, " + name)
print("How old are you, " + name + " p.s. put a zero infront of a single digit")
age = int(input())

if age >= 18:
    print("if you're " + str(age) + ", that means it's beer o'clock!")
diff = 18 - age
if age < 18:
    print("That means you have to wait " + str(diff) + " years to have a drink on me!")

The concatenation of str should not be done with + operator. If you work with int, float or other types, you've to convert them back to a str. Instead, use string formatting. With modern Python, we have f-strings. A f in front of the " introduces a format-string. The names in the curly braces are replaced with their values. For example, {age} is replaced with the age, which is an int.

print("hello world!")
print("What is your name?")
name = input()

print(f"That is a nice name {name}")
print(f"How old are you {name}")
age = int(input())

if age >= 18:
    print(f"if you're {age} that means it's beer o'clock!")
diff = 18 - age
if age < 18:
    print(f"That means you have to wait {diff} years to have a drink on me!")

The benefit is, that you don't have to convert the int explicit back to a str if you're using string formatting.