Operators and Operands

You can build complex expressions out of simpler ones using operators. Operators are special tokens that represent computations like addition, multiplication and division. The values the operator works on are called operands.

The following are all legal Python expressions whose meaning is more or less clear:

20 + 32
5 ** 2
(5 + 9) * (15 - 7)

The tokens +, -, and *, and the use of parentheses for grouping, mean in Python what they mean in mathematics.

The asterisk (*) is the token for multiplication and ** is the token for exponentiation.

Addition, subtraction, multiplication, and exponentiation all do what you expect.

Remember that if we want to see the results of the computation, the program needs to specify that with the word print. The first three computations occur, but their results are not printed out.

Division and Truncated Division

In Python 3, which we will be using, the division operator / produces a floating-point result (even if both arguments are integers; 4/2 = 2.0 just like 4.0 / 2.0 = 2.0).

If you want truncated division, which ignores the remainder, you can use the // operator (for example, 5//2 is 2).

Both division and truncated division produce a result of type float.

Modulo

The modulus operator, sometimes also called the remainder operator or integer remainder operator works on integers (and integer expressions) and yields the remainder when the first operand is divided by the second. In Python, the modulus operator is a percent sign (%). The syntax is the same as for other operators.

In the above example, 7 divided by 3 is 2 when we use integer division and there is a remainder of 1.

The modulus operator turns out to be surprisingly useful. For example, you can check whether one number is divisible by another—if x % y is zero, then x is divisible by y. You could also use the remainder to figure out if a number is even or odd.