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not Operator in Python | Boolean Logic

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Python not keyword is a logical operator that is usually used to figure out the negation or opposite boolean value of the operand. The Keyword ‘not’ is a unary type operator which means that it takes only one operand for the logical operation and returns the complementary of the boolean value of the operand. For example, if we give false as an operand to the not keyword we get true as the return value. 

Syntax: not var

How to Use Not Operator in Python?

The not operator is very easy to use. You just need to use the ‘not’ keyword in front of the variable. Let’s understand it better with an example:

Example: Basic example of not operator with true variable.

Python3




a = True
print(not a)


Output:

False

As you can see from the above example, we just used not operator to change the true value to false.

Practical Applications

The possible practical applications of the ‘not’ keyword are: 

  1. This keyword is mostly used for altering the boolean value.
  2. It is used with an if statement. It is used to negate the condition in the if statement, 
  3. The ‘not’ keyword is also used with ‘in keyword‘. It is used with the ‘in’ keyword when we are searching for a specific value in the collection of data.

More Examples on Not Operator

Let’s look at some examples of not operator in Python codes, each example shows different use-cases of not operator.

Python not operator with Variable

Basic example of not operator with variable.

Python3




# variable
a = False
print(not a)


Output:

True

Using the “not” Boolean Operator in Python with Specific condition

As basic property of the ‘not’ keyword is that it is used to invert the truth value of the operand. So we can see here that the result of every value is inverted from their true value. At #5 we can see the compare operation result would be false, so by negation of it we get the True value. Similarly, we can see all results are inverted.

Python3




# Python code to demonstrate
# 'not' keyword
 
# Function showing working of not keyword
def geek_Func():
   
    # 1 Not with False boolean value
    geek_x = not False
    print('Negation  of False : ', geek_x)
 
    # 2 Not with true boolean value
    geek_y = not True
    print('Negation of True : ', geek_y)
 
    # 3 Not with result of and operation
    geek_and = not(True and False)
    print('Negation of result of And operation : ', geek_and)
 
    # 4 Not with result of or operation
    geek_or = not(True or False)
    print('Negation of result of or operation : ', geek_or)
 
    # 5 Not with result of compare operation
    geek_Com = not (5 > 7)
    print('Negation of result of And operation : ', geek_Com)
 
 
geek_Func()


Output: 

Negation  of False :  True
Negation of True :  False
Negation of result of And operation :  True
Negation of result of or operation :  False
Negation of result of And operation :  True

Using the Not Operator with different Value

In this Code, we show the working of the ‘not’ operator with a different value other than boolean, and see how it works. 

Python3




# Python code to demonstrate
# 'not' keyword
 
# Function showing working of not keyword
def geek_Func():
   
    # Not with String boolean value
    geek_Str = "geek"
    print('Negation  of String : ', not geek_Str)
 
    # Not with list boolean value
    geek_List = [1, 2, 3, 4]
    print('Negation of list : ', not geek_List)
 
    # Not with dictionary
    geek_Dict = {"geek": "sam", "collage": "Mit"}
    print('Negation of dictionary : ', not geek_Dict)
 
    # Not with Empty String
    geek_EDict = ""
    print('Negation of Empty String : ', not geek_EDict)
 
    # Not with Empty list
    geek_EList = []
    print('Negation of Empty List : ', not geek_EList)
 
    # Not with Empty dictionary
    geek_EStr = {}
    print('Negation of Empty Dictionary : ', not geek_EStr)
 
geek_Func()


Output: 

Negation  of String :  False
Negation of list :  False
Negation of dictionary :  False
Negation of Empty String :  True
Negation of Empty List :  True
Negation of Empty Dictionary :  True

In the above example, we saw that treating all the data types as operands with not keyword., ‘not’ treats true to all the data types who had value and false to those who were empty value.

Logical NOT operator with the list

Here in this example, we are using Not operator with the list:

Python3




# Python code to demonstrate
# 'not' keyword
 
 
geek_list = [5, 10, 20, 59, 134, 83, 95]
 
# Function showing working of not keyword
def geek_Func():
   
    # Using not with if statement
    if not geek_list:
        print("Inputted list is Empty")
    else:
        for i in geek_list:
            if not(i % 5):
               
                # Using not with in statement
                if i not in (0, 10):
                    print("Multiple is not in range")
                else:
                    print(i)
            else:
                print("The number is not multiple of 5")
 
geek_Func()


Output: 

Multiple is not in range
10
MUltiple is not in range
The number is not multiple of 5
The number is not multiple of 5
The number is not multiple of 5
Multiple is not in range

We have covered the meaning, syntax, and uses of the not operator in Python. This might have given you the complete picture of what is not in Python. You can look at the above examples or experiment on your device about not operator. It is a very basic yet useful operator in Python.

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Last Updated : 20 Dec, 2023
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