How to Get a Negation of a Boolean in Python

Boolean datatype is the built-in data type in Python. It represents the True or False values. Like 0<1 is True and 7>10 is False. The task is to print the negation of a Boolean variable 

Input: True
Output: False 

Input: False
Output: True 

Input: "GeeksforGeeks" 
Output: False

Input: [True, True, False, True, False]
Output: [False, False, True, False, True]

To implement this task, Python has many built-in operators and functions. Let’s explore them one by one.

How to Get a Negation of a Boolean in Python Using the “~” operator

This is the Bitwise NOT operator which can be used to return the negation of the operand.

Python3

# Input boolean variable
a = False

# Print a
print(a)

# Printing negation
print(bool(~a))

Output : 

False
True

Time Complexity: O(1)
Auxiliary Space: O(1)

Negation of a Boolean in Python Using “not” Operator 

Not operator is the logical operator which returns the complementary of the Boolean value of the operand.

Python3

# Input boolean variable
a = False

# Print a
print(bool(a))

# Printing negation
print(not a)

Output : 

False
True

Time Complexity: O(1)
Auxiliary Space: O(1)

Here, we are using print(bool(a)), as if the “a” is not a Boolean value then it will be converted into it.

Let’s understand this with another example : 

Python3

# Input string
a = "GeeksforGeeks"

# Converting string into boolean
# Printing boolean value
print(bool(a))

# Printing negation
print(not a)

Output : 

True
False

Time Complexity: O(1)
Auxiliary Space: O(1)

Get a Negation of a Boolean in Python Using Operator Module

Before implementing the code, import the Operator module using below code.

import operator

This method uses the operator.not_() function to return the negation of the Boolean value. It has a constant time complexity and requires constant auxiliary space.

Python3

# Input string
a = "GeeksforGeeks"

# Converting string into boolean
# Printing boolean value
print(bool(a))

# Printing negation
print(operator.not_(a))

Output: 

True
False

Time Complexity: O(1)
Auxiliary Space: O(1)

We can also implement the negation in list elements using operator.not_() function

Python3

# Input list of boolean elements
input_list = [True, True, False, True, False]

# Printing list
print(list(input_list))

# Converting into negation values
# Mapping them with their input
# index values
output_list = map(operator.not_, input_list)

# Printing output list
print(list(output_list))

Output : 

[True, True, False, True, False]
[False, False, True, False, True]

Note: To negate the values in the python list, always use the above syntax. As operator.not_(input_list) will consider the whole list as an input and perform accordingly.

Time Complexity: O(n)
Auxiliary Space: O(n)

Get a Negation of a Boolean in Python Using Numpy Module

Before implementing the code, import the Numpy library using below code.

import numpy as np

This method uses the numpy library and has two functions: bitwise_not() and logical_not().

1. bitwise_not() function returns the negation value of the given Boolean argument.

Python3

# Input array of boolean elements
b = np.array([True, True, False, True, False])

# Printing input list
print(list(b))

# Converting using bitwise_not function
b = np.bitwise_not(b)

# Printing output list
print(list(b))

Output : 

[True, True, False, True, False]
[False, False, True, False, True]

Time Complexity: O(n)
Auxiliary Space: O(n)

2. We can also use logical_not() function, it is also the function of Numpy library and returns the Boolean value.

Python3

# Input boolean variable
b = True

# Printing input
print(b)

# Converting using logical_not()
# function
b = np.logical_not(b)

# Printing output
print(b)

Output : 

True 
False

Time Complexity: O(1)
Auxiliary Space: O(1)

Get a Negation of a Boolean in Python Minus the value with ‘1’:

This method subtracts the boolean data-type value to 1 and typecasts it back to boolean to get the negation of the original boolean value. It has a constant time complexity and requires constant auxiliary space.

Python

# Input boolean variable
b = True

# Printing input
print(b)

# Converting by subtracting 1
# function
b = bool(1-b)

# Printing output
print(b)

Output:

True
False

Time Complexity: O(1)
Auxiliary Space: O(1)