Beginning Python - From Novice to Professional

12 CHAPTER 1 ■ INSTANT HACKING: THE BASICS
Here 10/3 is 3 because the result is rounded down. But 3×3 is 9, so you get a remainder of
one. When you divide 9 by 3, the result is exactly 3, with no rounding. Therefore, the remainder
is zero. This may be useful if you want to check something “every 10 minutes” as in the recipe
earlier in the chapter. You can simply check whether minute % 10 is zero. (For a description on
how to do this, see the sidebar “Sneak Peek: The if Statement,” later in the chapter.) As you can
see from the final example, the remainder operator works just fine with floats as well.
The last operator is the exponentiation (or power) operator:
>>> 2 ** 3
8
>>> -3 ** 2
-9
>>> (-3) ** 2
9
Note that the exponentiation operator binds tighter than the negation (unary minus), so
-3**2 is in fact the same as -(3**2). If you want to calculate (-3)**2, you must say so explicitly.
Large Integers
Python can handle really large integers:
>>> 1000000000000000000
1000000000000000000L
What happened here? The number suddenly got an L tucked onto the end.
■Note If you’re using a version of Python older than 2.2, you get the following behavior:
>>> 1000000000000000000
OverflowError: integer literal too large
The newer versions of Python are more flexible when dealing with big numbers.
Ordinary integers can’t be larger than 2147483647 (or smaller than –2147483648); if you
want really big numbers, you have to use longs. A long (or long integer) is written just like an
ordinary integer but with an L at the end. (You can, in theory, use a lowercase l as well, but that
looks all too much like the digit 1, so I’d advise against it.)
In the previous attempt, Python converted the integer to a long, but you can do that yourself,
too. Let’s try that big number again:
>>> 1000000000000000000L
1000000000000000000L