Right-Aligned Number Triangle in Python

Beginner
⏱️ 5 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Spacing + Loops
Right-aligned number triangle output (1, 1 2, 1 2 3, ...) in Python

What You’ll Learn

How to print a right-aligned number triangle in Python. Each row prints numbers starting from 1 up to the row number, and leading spaces are used to align the triangle to the right.

This pattern teaches you how to combine spacing (alignment) with nested loops (row/column printing).

⭐ Pattern Output

For rows = 5, the pattern looks like this:

Output
    1
   1 2
  1 2 3
 1 2 3 4
1 2 3 4 5
1

Complete Python Program

First we print spaces to shift the row to the right. Then we print 1 through i with a trailing space for readability.

Python
rows = 5

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

🧠 How It Works

1

Choose the row count

rows = 5 sets the height of the triangle.

Setup
2

Outer loop (rows)

for i in range(1, rows + 1) prints one row at a time.

Row control
3

Print leading spaces

The loop for _ in range(rows, i, -1) prints rows-i spaces so the row becomes right-aligned.

Alignment
4

Print numbers 1..i

for k in range(1, i + 1) prints increasing numbers on each row using end=" ".

Number printing
=

Right-aligned triangle

Total printed numbers are 1+2+…+n = n(n+1)/2, so runtime is O(n²) for n rows.

2

Variation — User Input Version

Let the user choose the number of rows at runtime. The logic stays the same: print spaces, then print 1..i.

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

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

💡 Tips for Enhancement

Try These

  • Remove the trailing space by printing with end="" and adding your own separator
  • Print repeated numbers per row (like 1 1, 2 2 2)
  • Turn it into a centered pyramid by printing extra spaces between numbers
  • Reverse the triangle by counting the outer loop down
  • Replace numbers with letters to build alphabet patterns

Avoid

  • Forgetting the newline print() after each row
  • Mixing alignment and number-printing logic in one loop (harder to read)
  • Using tabs for spacing (results vary across consoles)
  • Assuming user input is always valid (wrap int() if needed)

Key Takeaways

1

Leading spaces create the right alignment.

2

The inner loop prints numbers from 1 to the current row i.

3

Total printed numbers follow n(n+1)/2.

4

The same alignment trick works for many other pyramid patterns.

❓ Frequently Asked Questions

The spaces shift each row to the right. As rows increase, spaces decrease, creating the right-aligned triangle.
Change print(k, end=" ") to print(k, end=""). You can also format multi-digit values with padding if needed.
Print more leading spaces and add consistent spacing between numbers (or fixed-width formatting) so the rows expand symmetrically.
O(n²) for n rows since total prints are 1+2+…+n.

Explore More Python Number Patterns!

Try left-aligned, right-aligned, and centered triangles to master nested loops.

All Number Patterns →
Did you know?

The total numbers printed in an increasing triangle of n rows is the triangular number n(n+1)/2.

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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