PythonOperatorsLogical Operators

Logical Operators

Logical operators (and, or, not) are used to combine or invert boolean values (True and False). They are essential for creating complex conditional logic that controls the flow of your programs.

The Core Logical Operators

and

The and operator returns True only if both of its operands are true.

ABA and B
TrueTrueTrue
TrueFalseFalse
FalseTrueFalse
FalseFalseFalse

Pyground

Check if a user is both an admin and is active.

Expected Output:

Can access dashboard? True
What if the user is not active? False

Output:



Truthiness: Beyond True and False


In Python, logical operators can work with any value, not just booleans. Every value in Python has an inherent “truthiness.”


    

  • Falsy Values: These values are treated as False in a boolean context.

      

    • None
      • 

    • False
      • 

    • 0 (of any numeric type, e.g., 0, 0.0, 0j)
      • 

    • Empty sequences and collections: '', [], (), {}, set()
      • 

    

    • 

  • Truthy Values: All other values are treated as True.
    • 



Pyground
Demonstrate truthiness with an empty list and a non-empty string.
Expected Output:
The list is empty, so it is 'falsy'.
The string 'Alice' is not empty, so it is 'truthy'.
Output:


Short-Circuit Evaluation


This is a crucial and powerful feature of the and and or operators. Python evaluates them from left to right and stops as soon as the result is determined.


    

  • A and B: If A is falsy, the whole expression must be false, so Python returns A and never evaluates B. If A is truthy, Python must evaluate B and returns B.
    • 

  • A or B: If A is truthy, the whole expression must be true, so Python returns A and never evaluates B. If A is falsy, Python must evaluate B and returns B.
    • 



Use Case 1: Guarding Against Errors


Short-circuiting is often used to prevent errors, like trying to divide by zero.


Pyground
Safely calculate a ratio only if the denominator is not zero.
Expected Output:
Result with denominator 0: 0
Result with denominator 20: 5.0
Output:


Use Case 2: Providing Default Values


The short-circuit behavior of or provides a concise way to select a default value.


Pyground
A user can provide a username, but if they leave it empty, default to 'Guest'.
Expected Output:
Username: Guest
Username: Riya
Output:


Combining with Comparison Operators


The most common use of logical operators is to build complex conditions by combining the results of comparison operators.


Pyground
Determine if a student is on the honor roll. They must have a GPA of 3.5 or higher AND not be on academic probation.
Expected Output:
GPA: 3.7, On Probation: False
Eligible for Honor Roll? True
Output:
Assignment & Compound OperatorsBitwise & Identity Operators