If NOT

Introduction:

  • Python supports the usual logical conditions from mathematics:
    • Equals: a == b
    • Not Equals: a != b
    • Less than: a < b
    • Less than or equal to: a <= b
    • Greater than: a > b
    • Greater than or equal to: a >= b

Using NOT:

  • The not keyword is a logical operator used to reverse the result of a conditional statement. It changes True to False and False to True.

Example:

  • Test if a is NOT greater than b:

    python
    a = 33
b = 200
if not a > b:
    print("a is NOT greater than b")

Syntax of If Statement with NOT:

python
if not value:
    statement(s)
  • The value can be of type boolean, string, list, dict, set, tuple, etc. The statements inside the if block execute only if the value is False or if the value (like a collection) is empty.

Examples:

  1. Python "if not" with Boolean:

    • Using not in the boolean expression of an if statement.

      python
      a = False

if not a:
    print('a is false.')
    • Output: a is false.
       
  2. Python "if not" with String:

    • Using if not to print the string only if the string is not empty.

      python
      string_1 = ''

if not string_1:
    print('String is empty.')
else:
    print(string_1)
    • Output: String is empty.

Summary:

  • In this tutorial, we learned how to use the NOT logical operator in conjunction with Python if conditional statements. Practice using if not to conditionally execute code based on the absence of a value or the falseness of a condition