1.2.1.4 PCEP-30-02 Practice Test Compendium – Operators

Operators

01) An operator is a symbol that determines an operation to perform. The operator along with its arguments (operands) forms an expression that is subject to evaluation and provides a result.

02) There are three basic groups of operators in Python:

• arithmetic, whose arguments are numbers;

• string, which operates on strings or strings and numbers;

• Boolean, which expects that their arguments are Boolean values.

03) A unary operator is an operator with only one operand.

04) A binary operator is an operator with two operands.

Unary arithmetic operators

Operator	Meaning	Example
-	Change argument's sign	-(-2) is equal to 2
+	Preserve argument's sign	+(-2) is equal to -2

Binary arithmetic operators (ordered according to descending priority)

Priority	Operator	Name	Example	Meaning	Result	Result Type
Highest	**	Exponentiation	2 ** 3	$2^3$	8	int if both arguments are ints float otherwise
	*	Multiplication	2 * 3	2 × 3	6	int if both arguments are ints float otherwise
	/	Division	4 / 2	4 ÷ 2	2.0	always float raises ZeroDivisionError when divider is zero
	//	Integer division	5 // 2		2	int if both arguments are ints float otherwise raises ZeroDivisionError when divider is zero
	%	Remainder (modulo)	5 % 2	5 mod 2	1	int if both arguments are ints float otherwise raises ZeroDivisionError when divider is zero
Lowest	+	Addition	2 + 1	2 + 1	3	int if both arguments are ints float otherwise
	-	Subtraction	2 - 1	2 − 1	1	int if both arguments are ints float otherwise

pairs of parentheses can be used to change the order of operations, for example:

• 2 + 3 * 4 evaluates to 24

• (2 + 3) * 4 evaluates to 20

when operators of the same priority (other than **) are placed side-by-side in the same expression, they are evaluated from left to right: therefore, the expression:

1 / 2 * 2

evaluates to 1.0, not to 0.25.

This convention is called left-sided binding.

when more than one ** operator is placed side-by-side in the same expression, they are evaluated from right to left: therefore, the expression:

2 ** 2 ** 3

evaluates to 256 ($2^8$), not to 64 ($4^3$) – this is right-sided binding.