How to Get a Negation of a Boolean in Python?

In this article, we will learn how to get a negation of a Boolean in Python.

In Python, the Boolean datatype is a built-in data type that represents True or False values. For example, 5<20 is True and 10>20 is False. Boolean negation means converting True to False and False to True.

The following are the various methods to accomplish this task ?

• Using the "not" operator

• Using the "~" operator

• Using operator module

• Using arithmetic subtraction from 1

• Using NumPy functions

Method 1: Using the "not" Operator

The not operator is the most common and pythonic way to negate a Boolean value. It returns the logical complement of the operand.

Example

The following program demonstrates Boolean negation using the not operator ?

# input boolean values
bool1 = True
bool2 = False

print("Original values:")
print("bool1 =", bool1)
print("bool2 =", bool2)

print("\nNegated values:")
print("not bool1 =", not bool1)
print("not bool2 =", not bool2)

# Works with expressions too
print("\nWith expressions:")
print("5 > 3 =", 5 > 3)
print("not (5 > 3) =", not (5 > 3))

Original values:
bool1 = True
bool2 = False

Negated values:
not bool1 = False
not bool2 = True

With expressions:
5 > 3 = True
not (5 > 3) = False

Method 2: Using the "~" Operator

The bitwise NOT ("~") operator performs bitwise negation. When used with Boolean values, it requires conversion using bool() to get the expected result.

Example

The following program returns the negation using the bitwise NOT operator ?

# input boolean value
input_bool = False

print("Input boolean value:", input_bool)

# Using ~ operator (requires bool() conversion)
negated = bool(~input_bool)
print("Negation using ~ operator:", negated)

# Demonstrating with True value
input_bool2 = True
print("\nInput boolean value:", input_bool2)
print("Negation using ~ operator:", bool(~input_bool2))

Input boolean value: False
Negation using ~ operator: True

Input boolean value: True
Negation using ~ operator: False

Method 3: Using Operator Module

The operator module provides the not_() function which performs logical negation equivalent to the not operator.

Example

The following program demonstrates negation using the operator module ?

import operator

# input values
input_bool = True
input_string = "tutorialspoint"

print("Boolean negation:")
print("Input:", input_bool)
print("Negated:", operator.not_(input_bool))

print("\nString negation (truthy to falsy):")
print("Input string:", input_string)
print("bool(input_string):", bool(input_string))
print("operator.not_(input_string):", operator.not_(input_string))

Boolean negation:
Input: True
Negated: False

String negation (truthy to falsy):
Input string: tutorialspoint
bool(input_string): True
operator.not_(input_string): False

Method 4: Using Arithmetic Subtraction from 1

For Boolean values (which are integers 0 and 1 in Python), subtracting from 1 effectively negates the value.

Example

The following program negates Boolean values using arithmetic subtraction ?

# input boolean values
input_bool1 = False
input_bool2 = True

print("Method: 1 - boolean_value")
print("Input:", input_bool1, "? Negated:", bool(1 - input_bool1))
print("Input:", input_bool2, "? Negated:", bool(1 - input_bool2))

# Showing the integer nature of booleans
print("\nBoolean as integers:")
print("False as int:", int(input_bool1))
print("True as int:", int(input_bool2))

Method: 1 - boolean_value
Input: False ? Negated: True
Input: True ? Negated: False

Boolean as integers:
False as int: 0
True as int: 1

Method 5: Using NumPy Functions

NumPy provides logical_not() and bitwise_not() functions for negating Boolean arrays and individual values.

Example

The following program demonstrates NumPy Boolean negation functions ?

import numpy as np

# Single boolean value
single_bool = False
print("Single value negation:")
print("Input:", single_bool)
print("logical_not():", np.logical_not(single_bool))

# Boolean array
bool_array = np.array([True, False, True, False])
print("\nArray negation:")
print("Input array:", bool_array)
print("logical_not():", np.logical_not(bool_array))
print("bitwise_not():", np.bitwise_not(bool_array))

Single value negation:
Input: False
logical_not(): True

Array negation:
Input array: [ True False  True False]
logical_not(): [False  True False  True]
bitwise_not(): [False  True False  True]

Comparison

Conclusion

The not operator is the most readable and efficient method for Boolean negation in Python. Use NumPy functions for array operations and operator.not_() for functional programming contexts.