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.

Method 1: 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)

Method 2: 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)

Method 3: 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)

Method 4: 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)

Method #5: 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)