Right-Aligned Triangle Star Pattern in Python

Beginner
⏱️ 8 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
spaces + stars per row
Right-aligned triangle star pattern output in Python programming

What You'll Learn

This program prints a right-aligned triangle. Each row begins with some spaces so the stars line up to the right edge.

For row i (starting at 1), print rows - i spaces, then print i stars.

⭐ Pattern Output

When you run the program with rows = 5:

Output
    *
   **
  ***
 ****
*****
1

Complete Python Program

Fixed rows = 5 version:

Python
rows = 5

for i in range(1, rows + 1):
    for _ in range(rows - i):
        print(" ", end="")
    for _ in range(i):
        print("*", end="")
    print()

🧠 How It Works

1

Setup

rows is the height. for i in range(1, rows + 1): walks each row; two inner loops print spaces then stars, both using print(..., end="") until the final print().

Setup
2

Padding: print(" ", end="")

for _ in range(rows - i): prints rows - i spaces so the star block shifts right while the right edge stays straight.

Right align
3

Stars: print("*", end="")

for _ in range(i): prints i asterisks—same count per row as Program 1, different offset. Or use print((" " * (rows - i)) + ("*" * i)) in one call.

Stars
4

New line

print() ends the row. Characters before the newline: (rows - i) + i = rows every time.

Line break
=

Right-aligned triangle

Star total n(n+1)/2; O(n²) output for n = rows, O(1) extra space. Full-width lines scroll horizontally in the green preview on narrow viewports.

2

Variation — User Input Version

Read rows from user input:

Python
rows = int(input("Enter the number of rows: "))

for i in range(1, rows + 1):
    print((" " * (rows - i)) + ("*" * i))

💡 Tips for Enhancement

Try These

  • Use string repetition to simplify the code: (" " * (rows - i)) + ("*" * i)
  • Print spaces between stars using "* " * i (and trim if needed)
  • Compare with Program 1 to understand alignment vs. shape
  • Try the inverted right-aligned triangle next (Program 4)
  • Validate input (reject rows < 1)

Avoid

  • Printing trailing spaces after the stars (they can look odd in monospace output)
  • Using tabs for alignment (console rendering differs)
  • Forgetting to reset end="" logic per row
  • Mixing spaces and other characters in the indentation
  • Assuming user input is always valid

Key Takeaways

1

Row i prints rows - i spaces and then i stars.

2

Leading spaces are what make the triangle right-aligned.

3

Python can build each row with string repetition for clean code.

4

Time complexity is O(n²) due to printing \(\Theta(n^2)\) characters.

5

This pattern is the right-aligned variant of the basic triangle.

❓ Frequently Asked Questions

Because row 1 prints rows - 1 spaces so the single star sits at the right edge.
Yes. For each row i, print (" " * (rows - i)) + ("*" * i).
It’s O(n²) for n rows, since printing spaces + stars across all rows is \(\Theta(n^2)\).

Next: Inverted Right-Aligned

Continue to Program 4 to print the inverted right-aligned triangle.

Program 4 →
Did you know?

Right-aligned patterns are a simple way to practice controlling leading spaces and understanding how alignment works in text output.

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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