Python Reference: Thirty-Four Operators in Python

1. About - Cover what operators are used for.
2. Math - Perform arithmetic while following PEMDAS.
3. Assignment - See how objects are named and incremented.
4. Boolean - Find True / False answers and create program logic.
5. Bitwise - Introduce operators performing on bit-level data.

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A Guide to Understanding Operators in Python

Beginner

Python Reference

This Python reference offers programmers a quick way to learn Python and also serves as a source for reminders.

While the version documented here is Python 3.5.3, most of this is suitable for other versions of Python 3. Check your version for details.

1. What are Python Operators For?

At the center of an expression like x = 5 sits the equal symbol which is an operator. Each of the 34 operators we cover here has a specific meaning and purpose. Those fluent in Python have memorized most of these, but it only takes an understanding of about 20 to do amazing things with Python.

The first step is to categorize them. We group Python operators into four groups, starting with easiest.

1. Math - For expressions involving arithmetic (7 operators).
2. Assignment - For creating and incrementing variables and objects by assigning values (8 operators).
3. Boolean - For the logical flow of programs where every expression results in a True or False outcome (13 operators).
4. Bitwise - For advanced uses like cryptography, embedded languages, theoretical math and graphics where operations are performed on bits, so 1s and 0s (6 operators).

2. Python Math Operators

There are 7 math operators in Python, also referred to as arithmetic operators elsewhere.

The following table lists operators by the order of operation for math, commonly referred to as PEMDAS. This order can be overridden with parentheses ( ), otherwise, calculations are processed from left to right.

Python Math Operators in Version 3.5.3

Operator	Priority	Purpose	Example
( )	High	Parentheses override order	(1 + 2) * 3 9
**	High	Exponent	3 ** 2 9
*	High	Multiplication	3 * 3 9
%	High	Division (Modulo) returns remainder	5 % 2 1
//	High	Division (Floor) ignores remainder	5 // 2 2
/	High	Division (Regular)	3 / 3 1
+	High	Addition	3 + 3 6
-	High	Subtraction	3 - 3 0

Please note, technically parentheses are not operators. Also, multiplication and division operators are grouped together, as are addition and subtraction.

3. Python Assignment Operators

One of the first concepts beginners learn in Python is variable assignment, as in x = 5.

Python also offers "augmented assignment" operators which provide a shorthand way to increment counts. These include a mathematical operation and an assignment together.

As an example, let's use the most common type used to increment a count up using addition. The long form would look like x = x + 1 with the shorthand version reading x += 1. Here, assuming we start with x = 5 the next count would be 6 from the mathematical operation of addition and an in-place assignment.

For the augmented assignment examples below assume x = 5. The answer shows the next count in the sequence.

Python Assignment Operators in Version 3.5.3

Operator	Priority	Purpose	Example
=	High	Basic variable assignment	x = 5
+=	High	Count up	x += 1 6
-=	High	Count down	x -= 1 4
*=	Mid	Count by multiplication	x *= 2 10
/=	Low	Count by division	x /= 5 1.0
//=	Low	Count by floor division	x //= 2 2
%=	Low	Count by modulo division	x %= 2 1
**=	Mid	Count by exponent	x **= 2 25

Recall that the division of an integer in Python 3 will result in a float.

Bitwise augmented assignment operators exist but are beyond our scope here.

4. Python Operators with Boolean Values

A series of operators resolve to True or False outcomes and here we organize them in three groups.

1. Comparison Operators
2. Logical Operators
3. Membership Operators

a. Python Comparison Operators

The == operator is a test for equality of values, whereas != tests for non-equality. The remaining four with greater than > and less than < symbols are similar to other programming languages.

The is and is not operators compare whether two objects occupy the same memory location. So objects of different types do not compare as equal.

Python Comparison Operators in Version 3.5.3

Operator	Priority	Purpose	Example
==	High	Equal to	3 == 3 True
!=	High	Not equal to	3 != 3 False
<	High	Less than	5 < 3 False
>	High	Greater than	5 > 3 True
<=	High	Less than or equal	3 <= 3 True
>=	High	Greater than or equal	3 >= 3 True
is	Low	Object equal to	x = 'abc' y = 'abc' x is y True
is not	Low	Object not equal to	x = 'abc' y = ['abc'] x is y False

b. Python Logical Operators

The and, or operators test compound expressions. These can be complex expressions or simply the Boolean values True and False as the examples in the table below demonstrate.

The not operator reverses a single Boolean Value, or a compound expression.

Python Logical Operators in Version 3.5.3

Operator	Priority	Purpose	Examples
and	High	True if both expressions are True	1) True and True True 2) True and False False 3) False and True False 4) False and False False
or	High	True if one expression is True	1) True or True True 2) True or False True 3) False or True True 4) False or False False
not	High	Opposite of the result from a single Boolean value or compound expression	1) not True False 2) not False True 3) not 5 == 5 False 4) not (5 == 5) and (4 == 4) False

All of the following are considered False.

• None
• Numeric types: 0, 0.0, 0j
• Empty sequences: "", '', (), []

c. Python Membership Operators

Membership operators test whether the value on the left is in the sequence (list, tuple, set, etc.) on the right.

Python Membership Operators in Version 3.5.3

Operator	Priority	Purpose	Example
in	High	True if value present	1 in [1, 2, 3] True
not in	High	True if value not present	'a' not in 'apple' False

5. Python Bitwise Operators

The least common type of operator in Python is the Bitwise type which only operates at the bit level, so 1s and 0s. These are commonly used when programming drivers, protocols and graphics at a low-level close to the processor in machine code or assembly languages.

An introduction can be found at the Wikipedia article Bitwise operation.

Because these are advanced features, summaries are provided.

Python Bitwise Operators in Version 3.5.3

Operator	Priority	Summary
&	Low	Bitwise AND performs a logical AND operation
|	Low	Bitwise OR performs a logical inclusive OR operation
^	Low	Bitwise XOR performs a logical exclusive OR operation
~	Low	Bitwise NOT performs a logical negation on each bit
>>	Low	Shift bits to the right
<<	Low	Shift bits to the left

Python also offers bitwise augmented assignment operators. See the official documentation for details.

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