6  Python Operators

Learning Objectives

• Know the different classes of operators and their hierarchy
• Understand that operators can be used beyond numerical data

6.1 What are Operators?

In computer science, operators are symbols or keywords used to perform operations on data and variables (operands), like calculations or comparisons. They are essential for building expressions in programming.

Operators are classified by the type of operation:

• Arithmetic Operators: Basic math operations (+, -, *, /).
• Logical Operators: Return True or False (AND, OR, NOT).
• Relational Operators: Compare values, returning boolean results (>, <, ==).
• Assignment Operators: Assign values to variables (=, +=).
• Bitwise Operators: Operate on bits (&, |, ^).
• Unary/Binary Operators: Work with one or two operands respectively.

Python has a rich set of operators that are classified into multiple categories

Good resources for python operators can be found at the following:

https://www.w3schools.com/python/python_operators.asp https://docs.python.org/3/library/stdtypes.html#boolean-operations-and-or-not

6.2 Arithmetic Operators

These operators perform basic arithmetic operations.

Operator	Description	Example	Applicable Data Types
+	Addition	a + b	int, float, complex, str, list, tuple, byte, bytearray
-	Subtraction	a - b	int, float, complex
*	Multiplication	a * b	int, float, complex, str, list, tuple, bytearray
/	Division	a / b	int, float, complex
%	Modulus (remainder)	a % b	int, float
**	Exponentiation	a ** b	int, float
//	Floor Division	a // b	int, float

6.3 Comparison (Relational) Operators

These operators compare two values and return a boolean (True or False).

Operator	Description	Example	Applicable Data Types
==	Equal to	a == b	int, float, str, list, tuple, set, frozenset, dict, range
!=	Not equal to	a != b	int, float, str, list, tuple, set, frozenset, dict, range
>	Greater than	a > b	int, float, str, range
<	Less than	a < b	int, float, str, range
>=	Greater than or equal to	a >= b	int, float, str, range
<=	Less than or equal to	a <= b	int, float, str, range

6.4 Logical Operators

Used to combine conditional statements.

Operator	Description	Example	Applicable Data Types
and	Logical AND (both must be true)	a and b	bool, int
or	Logical OR (either can be true)	a or b	bool, int
not	Logical NOT (negates boolean)	not a	bool, int

6.5 Assignment Operators

Used to assign values to variables, sometimes with an operation included.

Operator	Description	Example	Applicable Data Types
=	Assign	a = 5	All types
+=	Add and assign	a += 5	int, float, str, list, tuple, bytearray
-=	Subtract and assign	a -= 5	int, float
*=	Multiply and assign	a *= 5	int, float, str, list, tuple, bytearray
/=	Divide and assign	a /= 5	int, float
%=	Modulus and assign	a %= 5	int, float
**=	Exponentiate and assign	a **= 5	int, float
//=	Floor-divide and assign	a //= 5	int, float

6.6 Bitwise Operators

Perform operations at the bit level.

Operator	Description	Example	Applicable Data Types
&	Bitwise AND	a & b	int, byte, bytearray
|	Bitwise OR	a | b	int, byte, bytearray
^	Bitwise XOR	a ^ b	int, byte, bytearray
~	Bitwise NOT	~a	int, byte, bytearray
<<	Left shift	a << 2	int, byte, bytearray
>>	Right shift	a >> 2	int, byte, bytearray

6.7 Membership Operators

Used to check membership within sequences (like strings, lists, tuples).

Operator	Description	Example	Applicable Data Types
in	True if value is present	‘a’ in ‘apple’	str, list, tuple, set, frozenset, dict, range
not in	True if value is not present	‘b’ not in ‘apple’	str, list, tuple, set, frozenset, dict, range

6.8 Identity Operators

Used to compare memory locations of two objects.

Operator	Description	Example	Applicable Data Types
is	True if both refer to same object	a is b	All types
is not	True if not same object	a is not b	All types

6.9 Unary Operators

Operate on a single operand.

Operator	Description	Example	Applicable Data Types
-	Negation (unary minus)	-a	int, float, complex
+	Unary plus	+a	int, float, complex
not	Logical NOT	not a	bool, int

6.10 Set Operators

Set-specific operators.

Operator	Description	Example	Applicable Data Types
|	Union (combine sets)	a | b	set, frozenset
&	Intersection (common)	a & b	set, frozenset
-	Difference (in a not in b)	a - b	set, frozenset
^	Symmetric difference	a ^ b	set, frozenset

6.11 Order of Precedence for operators

Operators are ordered in precedence in code (think BODMAS). Using parentheses can add clarity to code.

Use the table below to see the order:

Precedence Level	Operator(s)	Description	Example
1 (Highest)	()	Parentheses (brackets) for grouping expressions	(a + b) * c
2	**	Exponentiation	a ** b
3	+x, -x, ~x	Unary plus, unary minus, bitwise NOT	+a, -a, ~a
4	*, /, //, %	Multiplication, division, floor division, modulus	a * b, a / b
5	+, -	Addition, subtraction	a + b, a - b
6	<<, >>	Bitwise left shift, right shift	a << b, a >> b
7	&	Bitwise AND	a & b
8	^	Bitwise XOR	a ^ b
9	|	Bitwise OR	a | b
10	in, not in	Membership operators	'a' in 'apple'
11	<, >, <=, >=, ==, !=	Comparison operators	a < b, a == b
12	is, is not	Identity operators	a is b
13	not	Logical NOT	not a
14	and	Logical AND	a and b
15	or	Logical OR	a or b
16 (Lowest)	=, +=, -=, *=, /=,	Assignment operators	a = 5
	//=, %=, **=, &=, ^=,		a += 5
	\|=, <<=, >>=

6.12 Summary

Use the above tables to find operators you can use in python. Operators can make code more concise and readable, and can be intuitive to those not familiar with python functions. On the other hand operators can make code less readable and understandable in some situations when compared to utilising functions. Operators also cannot generally be passed as arguments into higher order functions. Operators behave differently on different data types. Try using the * operator to multiply two integers, and to multiply a string by an integer. We will use operators more in the next sections.

Key Points

• Python is rich in operators
• Operators can behave differently when used with different data types and structures
• Operators are ordered in precedence in code in the same way as in mathematics