The “If not” syntax in Python explained

In this Python tutorial, we will discuss the if not Syntax in Python programming language.

But before that let’s learn about the if and not operators one by one, then we will discuss what is if not Syntax in Python, and why is it used or what are its best use cases?

Table if Contents

The “not” operator in Python

The not operator in Python, is used to perform the logical Not operation in Python. The not is used to manipulate the Boolean values, or to changes True into False and False into True. This logical operator returns True if the statement is not True, but the value of the variable does not change. See an Example code below:

CODE :

# initialized a boolean value.
a = True

# type() will print the data type of var a which happens to be of class Boolean.
print('Data Type of var a :',type(a),'& value of var a is: ',a)

# using Not operator to change the boolean value.
print(not a)

print(a)

OUTPUT :

Data Type of var a : bool'> & value of var a is: True
False
True

In the above example, the not operator has been used to change the value of var a but the boolean value does not change permanently.

The “if” statement in Python

If statement is a conditional statement, that is used in every programming language. This is used to execute a command if certain criteria is matched, which is inside the indentation/block of the if block.

Now we will discuss “If not” syntax in Python Programming language.

The “If not” statement in Python

In Python, we can use the if conditional and not operator together. These are mainly used in two case scenario which are:

• To change the output of If conditional : As we know the not operator changes/alters the value of Boolean, like if a given boolean is True, the not operator will return it as false. When used it with the if block, the not operator alters/changes the output of if block.

See an example below:

CODE :

# initialized some variables with integers values.
b = 10
c = 2
d = b+c 

print('Sum of b+c :', d)

if d > 10:
    print('D is greater than 10')
else:
    print(' D is not greater than 10')

if not d > 10:
    print('D is greater than 10')
else:
    print('D is not greater than 10')

OUTPUT :

Sum of b+c : 12
D is greater than 10
D is not greater than 10

In the above example, the d is greater than 10. In the if-else block, you can see the if block gets executed because the if block says d > 10. Now in another if-else block which has not operator in the if block, you can see the else block gets executed here. This is because if with not operator alters the return value to False. Here, If statement returns True for d>10 but the not operator alters/changes it to False and python thinks d < 10 and that’s why code moves to else block. Below is another code example.

CODE :

b = 10
c = 2

d = b+c 

if not d < 10:
    print('D is greater than 10.')
else:
    print('D is not greater than 10.')

OUTPUT :

D is greater than 10.

Now in the above example, the d is greater than 10, but the if-not return False, which would have been True in the case of if operator only.

• To check if given variable is empty or not : “if not” syntax can also be used to check if the given variable is empty or not. See an example code below.

CODE :

When given variable is not empty.

# initialized a list and some variables with integer values.
a = [2,3,4]
b = 10
c = 2

# Checking if a is empty.
if not a:
    print(b+c)
else:
    # executes else block if Not empty. 
    print(a)

OUTPUT :

[2, 3, 4]

CODE :

When the given variable is empty

# initialized a list and some variables with integer values.
a = [2,3,4]
b = 10
c = 2

# Initialized an empty list. 
d = []

# Checking if a is empty.
if not d:
    print(b+c)
else:
    # executes else block if Not empty. 
    print(a)

OUTPUT :

12

Summary

In this Python tutorial, we learned about If statement and not statements. Also we learned about “if-not” syntax in Python programming language. The not operator changes the value to True if the Statement is False and vice-versa. Python considers all objects to be True. If the objects are numeric zero or an empty container than it considers them as False.

In the above examples, we saw that the when if-not used together, it alters the return value to opposite and also this can be used to check if the given object is empty or not. We suggest you to make modifications in the above examples, and test them for better understanding. Thanks.