Python Program to Print Hollow Diamond Star Pattern

Introduction

A hollow diamond pattern is formed by two symmetric triangular patterns—one upright and the other inverted—with stars (*) printed along the boundary and spaces inside, giving it a hollow effect. This exercise helps in understanding how to control loops and use conditional logic to print stars and spaces.

Problem Statement

Create a Python program that:

• Accepts the number of rows (half the height of the diamond).
• Prints a hollow diamond-shaped pattern using stars (*).

Example:

• Input: rows = 5
• Output:

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

Solution Steps

1. Input the Number of Rows: The user specifies the number of rows, which determines half the height of the diamond.
2. Use Nested Loops: The outer loops control the rows, and the inner loops handle printing the stars and spaces for both the upper and lower parts of the diamond.
3. Conditionally Print Stars and Spaces: Stars are printed on the boundary of the diamond, and spaces are printed inside to create the hollow effect.

Python Program

# Step 1: Input the number of rows for half the diamond
rows = int(input("Enter the number of rows: "))

# Step 2: Print the upper part of the diamond
for i in range(1, rows + 1):
    # Print leading spaces for alignment
    print(" " * (rows - i), end="")
    
    # Print stars and spaces for the hollow pattern
    for j in range(1, 2 * i):
        if j == 1 or j == 2 * i - 1:
            print("*", end="")
        else:
            print(" ", end="")
    print()

# Step 3: Print the lower part of the diamond
for i in range(rows - 1, 0, -1):
    # Print leading spaces for alignment
    print(" " * (rows - i), end="")
    
    # Print stars and spaces for the hollow pattern
    for j in range(1, 2 * i):
        if j == 1 or j == 2 * i - 1:
            print("*", end="")
        else:
            print(" ", end="")
    print()

Explanation

Step 1: Input the Number of Rows

• The program starts by asking the user for the number of rows, which defines half the height of the diamond (the upper part).

Step 2: Print the Upper Part of the Diamond

• The outer loop handles the number of rows for the upper triangle of the diamond.
  • The first part prints spaces to align the stars to form a triangular shape.
  • The second part conditionally prints stars (*) at the boundaries (first and last position of each row), while spaces are printed inside to create the hollow effect.

Step 3: Print the Lower Part of the Diamond

• The outer loop controls the rows for the lower triangle of the diamond, which is inverted.
  • The same logic is applied for spaces and stars, but this time the loop decreases to form the inverted triangle.

Output Example

For rows = 5, the output will be:

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

For rows = 4, the output will be:

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

Conclusion

This Python program prints a hollow diamond pattern using stars (*). The program uses nested loops to print the upper and lower parts of the diamond, with conditional logic to print stars at the boundary and spaces inside to create the hollow effect. This exercise helps in practicing loop control and formatting output in Python.