Operators

We already saw that we can do addition with +. But Python knows much more than that. Let’s take a closer look at what we can do with numbers

a = 17
b = 5

print(a + b)   # addition
print(a - b)   # subtraction
print(a * b)   # multiplication
print(a / b)   # division

Output

Nothing too crazy so far. + - * behave exactly like in math. The only "interesting" one is /, since 17 / 5 gives back 3.4 (a number with decimals), not 3

But what if we only want the whole part of the division? 17 / 5 = 3 with a remainder of 2. We have a special operator for that

a = 17
b = 5
print(a // b)   # integer division

This will print 3. We threw away the remainder. // is called integer division

And what if we only want the remainder? Same idea, different operator

a = 17
b = 5
print(a % b)   # remainder (modulo)

This will print 2. The % operator gives us the remainder of the division. It’s called the modulo operator. Don’t worry about the name, just remember what it does :)

% is extremely useful. For example, how do we know if a number is even? An even number is one that divides by 2 with no remainder. So n % 2 == 0 means n is even

n = 10
if n % 2 == 0:
    print("even")
else:
    print("odd")

There is one more operator, used for powers

print(2 ** 3)   # 2 to the power of 3

This will print 8, because 2 _ 2 _ 2 = 8. The ** operator means power. So 5 ** 2 is 25, 3 ** 4 is 81, and so on

A very important detail is the order of operations. Python respects math rules: multiplication and division happen before addition and subtraction

print(2 + 3 * 4)    # 14, not 20
print((2 + 3) * 4)  # 20

Just like in math, parentheses () force what to do first. When in doubt, add parentheses. They make the code easier to read anyway

Mission: The Calculation Panel

The station receives two numbers and must display the result of each operation. Read two integers a and b (you may assume b is not 0), then print, one per line, in this order:

the sum (a + b)
the difference (a - b)
the product (a * b)
the division (a / b)
the integer division (a // b)
the remainder (a % b)
a to the power of b (a ** b)

Example

If the user types

17
5

the program prints something like