Print First Row, Last Column, and Upper Triangle Including Main Diagonal in Python

Program Overview

This Python program reads an integer n between 1 and 80 and prints a square pattern of size n × n using asterisks (*).
The output highlights three specific parts of the square:
- The first row
- The last column
- All elements on and above the main diagonal (i ≤ j)
If n = 0 is entered, the program displays nothing.

Python Code:

# Read n from user
n = int(input("Enter a number between 1 and 80: "))

# Validate input
if 1 <= n <= 80:
    for i in range(n):
        row = ''
        for j in range(n):
            if i == 0 or j == n - 1 or i == j or i < j:
                row += '* '
            else:
                row += '  '
        print(row)
elif n == 0:
    pass  # No output for n = 0
else:
    print("The number must be between 0 and 80.")

Sample Output for n = 5:

* * * * *  
    *   *  
      *   *  
        *   *  
          * *  

Step-by-Step Explanation:

- The user inputs a number n
- If n = 0, the program does nothing
- If n is between 1 and 80, a nested loop prints each row and column
- A star is printed if the position is on:
— The first row (i == 0)
— The last column (j == n - 1)
— The main diagonal (i == j)
— Above the main diagonal (i < j)
- Otherwise, spaces are printed to maintain alignment