Use the if not Condition in Python

Use the if not Condition in Python

Najwa Riyaz Jul-13, 2021 Jun-07, 2021 Python Python Condition
  1. True and False Values in Python
  2. Examples of the if not Condition in Python

The if statement is combined with the not logical operator to evaluate if a condition did not happen. This article explains how to use the if not condition in Python.

Here’s a code block that demonstrates this condition.

if not a_condition:
    block_of_code_to_execute_if_condition_is_false

In the case above, the code block_of_code_to_execute_if_condition_is_false will be executed successfully if the result of a_condition is False.

True and False Values in Python

Before we begin, let us understand that the equivalent value is False in Python in the following cases:

  • Numeric zero values, such as 0, 0L,0.0
  • Empty sequences such as:
    • empty list []
    • empty dictionary {}
    • empty string ''
    • empty tuple
    • empty set
    • a None object

Examples of the if not Condition in Python

Here are several examples that help you understand how if not is utilized in Python.

Usage of Boolean Values

if not False:
    print ("not of False is True.")
if not True:
    print ("not of True is False.")

Output:

not of False is True.

Usage of a numeric Value

For example, values like 0, 0L,0.0 are associated with the value False.

if not 0:
    print ("not of 0 is True.")
if not 1:
    print ("not of 1 is False.")

Output:

not of 0 is True.

Usage of List of Values

if not []:
    print ("An empty list is false. Not of false =true")
if not [1,2,3]:
    print ("A non-empty list is true. Not of true =false")

Output:

An empty list is false. Not of false =true

Usage of Dictionary Values

if not {}:
    print ("An empty dictionary dict is false. Not of false =true")
if not  {
  "vehicle": "Car",
  "wheels": "4",
  "year": 1998
   }:
    print ("A non-empty dictionary dict is true. Not of true =false")

Output:

An empty dictionary dict is false. Not of false =true

Usage of String of Values

if not "":
    print ("An empty string is false. Not of false =true")
if not "a string here":
    print ("A non-empty string is true. Not of true =false")

Output:

An empty string is false. Not of false =true

Usage of a None Value:

if not None:
    print ("None is false. Not of false =true")

Output:

None is false. Not of false =true

Usage of set of Values:

   dictvar = {}
   print("The empty dict is of type", type(dictvar))
   setvar= set(dictvar)
   print("The empty set is of type",type(setvar))
   if not setvar:
       print ("An empty set is false. Not of false =true")

Output:

   The empty dict is of type <class 'dict'>
   The empty set is of type <class 'set'>
   An empty dictionary dict is false. Not of false =true

Usage of a tuple of Values

An Empty Tuple Is Associated With the Value False.

if not ():
    print ("1-An empty tuple is false. Not of false =true")
if not tuple():
    print ("2-An empty tuple is false. Not of false =true")

Output:

1-An empty tuple is false. Not of false =true
2-An empty tuple is false. Not of false =true

Related Article - Python Condition

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