Guess the Number - Invent Your Own Computer Games with Python - page 42

Converting Strings to Integers with the int() Function
15. guess = int(guess)
In line 15, we call a new function called int() . The int() function takes one
argument. The input() function returned a string of text that player typed. But in our
program, we will want an integer, not a string. If the player enters 5 as their guess, the
input() function will return the string value '5' and not the integer value 5 . Remember
that Python considers the string '5' and the integer 5 to be different values. So the int()
function will take the string value we give it and return the integer value form of it.
Let's experiment with the int() function in the interactive shell. Try typing the
following:
>>> int('42')
42
>>> int(42)
42
>>> int('hello')
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
int('forty-two')
ValueError: invalid literal for int() with base
10: 'hello'
>>> int('forty-two')
Traceback (most recent call last):
File "<pyshell#5>", line 1, in <module>
int('forty-two')
ValueError: invalid literal for int() with base
10: 'forty-two'
>>> int(' 42 ')
42
>>> 3 + int('2')
5
We can see that the int('42') call will return the integer value 42 , and that int
(42) will do the same (though it is kind of pointless to convert an integer to an integer).
However, even though you can pass a string to the int() function, you cannot just pass
any string. For example, passing 'hello' to int() (like we do in the int('hello')
call) will result in an error. The string we pass to int() must be made up of numbers.
The integer we pass to int() must also be numerical, rather than text, which is why