not Operator in Python

Last Updated : 17 Jul, 2026

The not keyword is a logical operator used to reverse the Boolean value of a condition or expression. It returns True if the operand is False, and returns False if the operand is True.

Python 
a = True
print(not a)

Output
False

Explanation: The value of a is True. Applying the not keyword reverses it to False, which is printed as the output.

Syntax

The general syntax of the not keyword is shown below:

not condition

Or, it can be used inside an if statement as follows:

if not condition:
# code

Truth Table

The following truth table shows the result of the not keyword for different Boolean values.

ConditionResult
TrueFalse
FalseTrue

Explanation: The not keyword always returns the opposite Boolean value of the given condition.

With Boolean Expressions

The not keyword can also be used with Boolean expressions to reverse their result.

Python 
print(not False)
print(not True)
print(not (5 > 7))
print(not (10 > 5))

Output
True
False
True
False

Explanation:

  • not False returns True.
  • not True returns False.
  • 5 > 7 is False, so not (5 > 7) returns True.
  • 10 > 5 is True, so not (10 > 5) returns False.

In Conditional Statements

The not keyword is commonly used in if statements to execute code when a condition is False.

Python 
log = False
if not log:
    print("Please log in")

Output
Please log in

Explanation: The value of log is False. Therefore, not log becomes True, so the print() statement is executed.

With Different Data Types

The not keyword can also be used with different data types. In Python, empty values are considered False, while non-empty values are considered True.

Python 
print(not "Python")
print(not "")
print(not [1, 2, 3])
print(not [])

Output
False
True
False
True

Explanation:

  • A non-empty string ("Python") is truthy, so not returns False.
  • An empty string ("") is falsy, so not returns True.
  • A non-empty list is truthy, so not returns False.
  • An empty list is falsy, so not returns True.

Checking Whether a List is Empty

The not keyword provides a simple way to check whether a list is empty.

Python 
num = []
if not num:
    print("The list is empty")
else:
    print("The list is not empty")

Output
The list is empty

Explanation: An empty list is treated as False in Python. Therefore, not numbers becomes True, and the first print() statement is executed.

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