Inverted Repeating Number Triangle Pattern in Python

Beginner

⏱️ 8 min read

📚 Updated: Aug 2026

🎯 3 Code Examples

🚀 Live Preview

Nested Loops

Inverted repeating number triangle output (55555, 4444, 333, 22, 1) in Python programming

Overview

What You’ll Learn

The inverted repeating number triangle widens first then shrinks: digit i repeats exactly i times — nested loops, print(..., end="") vs print(), and a clear visual result. This tutorial covers the shape rule, loop structure, a live preview, algorithm steps, worked Python examples, edge cases, and complexity.

Shape Rule

digit i repeats exactly i times

Row rows prints rows repeated rows times, then each next row repeats its digit fewer times down to a single 1.

Outer Loop

Rows

for i in range(rows, 0, -1): walks each line from the longest down to one digit.

Inner Loop

Digits

for j in range(1, i + 1): prints digit i exactly i times on that row.

print end= vs print()

Same line / next line

Repeated digits use print(i, end=""); end each row with print().

Live Preview

1–20 rows

Pick a row count and draw the inverted repeating number triangle instantly in the browser.

O(n²)

Complexity

Total digit prints still = n(n+1)/2; extra memory stays O(1).

Introduction

An inverted repeating number triangle pattern starts with the widest row and loses one repeat each line as the digit decreases. Each row prints the same digit multiple times; the repeat count shrinks while the digit value shrinks.

In Python you usually solve it with two nested for loops: the outer loop picks the digit, the inner loop repeats it with print(i, end=""), then print() moves to the next line.

Why it matters?

It pairs naturally with Program 10 in Python courses. Once nested loops and print(..., end="")/print() click, pyramids, diamonds, and hollow shapes become much easier.

Key Highlights

Row = Repeat Count

On row i, print digit i exactly i times.

Two Nested Loops

Outer picks the digit; inner controls how many times it repeats.

Print Then Break

print(i, end="") in the inner loop; print() after.

Series Foundation

Gateway to Program 10 (5, 44, 333, …) and Program 12.

In short: for each row i from rows down to 1, repeat print(i, end="") exactly i times, then call print().

Foundation

📝 Problem & Approach

Given a positive integer rows, print an inverted repeating number triangle: row i repeats digit i exactly i times, with the outer loop counting from rows down to 1.

Python

# First 5 rows (conceptual shape)
# 55555
# 4444
# 333
# 22
# 1
for i in range(rows, 0, -1):
    for j in range(1, i + 1):
        print(i, end="")   # digit i, repeated i times
    print()                # next row

Inputs & Outputs

Item	Type	Description
`rows`	int	Number of triangle lines to print (typically ≥ 1).
Printed output	text	Each row repeats one digit; the top row has `rows` copies of `rows`, the bottom row has a single `1`.

Minimal workflow

Pseudocode

for i from rows down to 1:
    repeat i times:
        print i (no newline)
    print newline

Approach comparison

Approach	Idea	Best for
Nested loops	Outer digit + inner repeats	Learning and interviews
`str(i) * i` in inner loop	Print a full repeated row with `str(i) *`	Leaner Python style once loops are understood

Cheat Sheet

⚡ Quick Reference

Goal	Pattern
Walk each row	`for i in range(rows, 0, -1):`
Repeat digit `i`	`for j in range(1, i + 1): print(i, end="")`
End the row	`print()`
One-line row shortcut	`str(i) * i` repeated per row
Program 10 variant	`for j in range(rows, i - 1, -1): print(i, end="")` (descending repeats)

Compare

📋 print end= vs print() vs str(i) *

Same triangle — different ways to emit characters.

print(i, end="")

same line

Prints a digit without moving to the next line

print()

new line

Ends the current row after all digits are printed

str(i) * i

one digit

Writes digit i when i is 1..9 — no format string

Learning tip

loops first

Master nested loops before the str(i) * shortcut

Context

When This Pattern Shows Up

Reach for this triangle when teaching or testing nested-loop basics.

First lab exercise
Most Python pattern series start here before pyramids and diamonds.
Nested-loop warm-up
Outer/inner bound practice with an immediate visual check.
Console I/O practice
Combine loops with input() for a flexible row count.
Gateway to variants
Compare Program 10 (5, 44, 333, …) and Program 12 next.
Not a UI layout tool
This is a console teaching pattern — not how you build modern app screens.

Key benefit: one small program that locks in nested loops, output sequencing, and O(n²) thinking.

Interactive

🔮 Live Preview

Choose a row count between 1 and 20 and draw the inverted repeating number triangle in the browser.

Hands-On

Examples Gallery

Three complete Python programs — fixed row count, input(), and a str(i) * shortcut. Click View Output to reveal sample console results.

📚 Getting Started

Print five rows of the inverted repeating number triangle with nested loops.

Example 1 — Fixed `rows = 5`

Hard-coded height — outer picks digit, inner repeats it i times.

Python

rows = 5

for i in range(rows, 0, -1):
    for j in range(1, i + 1):
        print(i, end="")
    print()

How It Works

When i = 5, the inner loop runs five times and prints 55555. When i = 4, it prints 4444, and so on until i = 1 prints 1. print() after the inner loop starts the next row.

📈 Practical Variant

Let the user choose the height at runtime.

Example 2 — User Input Version

Read the row count with input() and int() (wrap in try/except ValueError in real apps).

Python

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

for i in range(rows, 0, -1):
    for j in range(1, i + 1):
        print(i, end="")
    print()

How It Works

Same nested-loop core as Example 1; only the source of rows changes. Non-numeric input raises ValueError with bare int(input()) — use try/except for safer labs.

⚡ Shortcut Style

Same shape without an explicit inner repeat loop.

Example 3 — `str(i) * i`

Build each row with str(i) * i, then print it.

Python

rows = 5

for i in range(rows, 0, -1):
    print(str(i) * i)

How It Works

str(i) * i creates a string of repeated digit i. Great once you understand the nested-loop idea; keep the two-loop version for exams that ask you to show both bounds.

🧠 How the Algorithm Prints Rows

Set up

print() is built in; use input() when reading input. Set rows (fixed or from input).

Setup

Outer loop (rows)

for i in range(rows, 0, -1): picks the digit; the inner loop prints it i times.

Row

Inner loop (repeats)

for j in range(1, i + 1): repeats digit i exactly i times with print(i, end="").

Repeats

New line

print() ends the row so the next outer iteration starts fresh.

Break

Triangle complete

Total digit prints: 1+2+…+n = n(n+1)/2 — O(n²) time, O(1) extra memory.

Trace

🔎 Worked Walkthrough — `rows = 4`

Trace each outer-loop value of i and count how many times the inner loop prints digit i.

`i`	Inner `j` range	Repeats	Printed row
`4`	`1..4`	4	`4444`
`3`	`1..3`	3	`333`
`2`	`1..2`	2	`22`
`1`	`1..1`	1	`1`

Total digit prints: 1 + 2 + 3 + 4 = 10 = 4×5/2.

Use Cases

Where this tiny pattern (and its loop structure) shows up beyond the homework prompt.

1. Teaching Nested Loops

Clearest visual proof that outer and inner bounds interact.

Example: change j <= i and watch the shape change.

2. Pattern Series Base

Foundation for inverted, pyramid, diamond, and hollow variants.

Example: Program 10 uses for j in range(rows, i - 1, -1) so repeats grow as the digit shrinks.

3. Console Formatting Drills

Practice print vs row newline without complex math.

Example: put print() inside the inner loop by mistake.

4. Character Substitution

Swap digits for letters, stars, or spaced output once the loop works.

Example: print i + " " for spaced repeated digits on each row.

5. Complexity Intuition

Triangular totals make O(n²) concrete for beginners.

Example: count printed digits for n = 10 still → 55.

6. Input Validation Labs

Pair the pattern with input() and positive-row checks.

Example: reject rows <= 0 and re-prompt.

Pro Tip: when an interviewer asks for patterns, explain the outer/inner roles first — then write the loops. The story matters as much as the code.

Advantages

Why this pattern earns a permanent spot in beginner C courses.

1. Instant Visual Feedback
Wrong bounds show up immediately as a broken staircase.
2. Minimal Concepts
Only loops and console output — no arrays or math libraries.
3. Easy to Extend
Invert, center, hollow, or change the fill character with small edits.
4. O(1) Extra Memory
Streaming output needs no storage beyond loop counters.

Pro Tip: learn the nested-loop version first; treat str(i) * i as a polish shortcut afterward.

Usage Tips

Small habits that keep number-pattern code clean.

1. Name Bounds Clearly
Use rows (or n) and keep i/j for row/column — or rename to row/col.
2. Prefer try/except ValueError
Avoid crashes when the user types letters instead of a number.
3. Keep print() Outside
Only call print() after the inner loop finishes the row.
4. Use j <= i for Repeat Count
for j in range(1, i + 1): with print(i, end="") repeats digit i exactly i times.
5. Dry-Run One Small n
Trace rows = 3 on paper before coding larger demos.

Pro Tip: if the output is a vertical list of single digits per line, you almost certainly put print() inside the inner loop.

Common Pitfalls

Mistakes that commonly break inverted repeating number patterns.

1. print() Inside the Inner Loop
Each repeated digit lands on its own line — you get a column, not a triangle.
→ Use print(i, end="") for repeats; print() only after the inner loop.
2. Wrong Inner Bound
Using for j in range(rows, i - 1, -1) builds Program 10 (5, 44, 333…). Using range(1, rows + 1) on every row prints a rectangle.
→ For this shape, keep for j in range(1, i + 1) so digit i repeats exactly i times.
3. Forgetting the Row Break
Omitting print() glues every repeat onto one endless line.
→ Always end the row after the inner loop.
4. Blind int(input())
Letters or empty input raise ValueError with bare int(input()).
→ Catch ValueError and re-prompt on failure.
5. Off-by-One on 0-Based Loops
Switching to i = 0 without adjusting the digit and repeat count prints an empty first row or wrong counts.
→ Prefer 1-based range(rows, 0, -1) with range(1, i + 1), or carefully map both values if you go 0-based.

Edge Cases

Check these inputs before calling the solution done.

rows = 1

Single repeated digit

Output is just one copy of rows on one line.

rows = 0

Empty pattern

Outer loop never runs — print nothing or show a message.

Negative

`rows < 0`

Treat as invalid; re-prompt instead of silent empty output.

Large n

Many rows

Output grows as n²/2 characters — fine for labs, noisy for huge n.

Bad input

Non-numeric input()

int(input()) raises ValueError — validate first.

Fill char

Inner bound j <= rows by mistake

Use j <= i so row i repeats exactly i times.

Drill

🎯 Practice Problems

Try these variations to lock in the pattern.

1. Descending repeating triangle

Inner loop j from rows down to i (see Program 10)
Continue with Program 10

2. Program 12 follow-up

Use for i in range(rows, 0, -1): as outer loop
Shows the loop structure is reusable

3. Safe input loop

Validate rows >= 1 after int(input())
Then draw the triangle

4. Same digit, different count

Use print(i, end="") between repeated digits
Harder follow-up after this page

Important

Notes

Triangular count. Total digit prints for n rows is n(n+1)/2 — hence O(n²) time.
print(..., end="") stays on the line; print() advances — mix them carefully.
Validate rows > 0 for interactive programs; rows = 1 should print rows copies of the top digit.
This page is left-aligned. Centered pyramids need leading spaces — covered later in the series.

Quick Takeaway: outer loop picks the row, inner loop repeats digit i, then break the line — that is the whole pattern.

Analysis

⏱️ Time and Space Complexity

Program	Time	Extra space
Nested loops (Examples 1–2)	`O(rows²)`	`O(1)`
`str(i) * i` (Example 3)	`O(rows²)`	`O(rows)` per row string (temporary)

Wrap Up

🎉 Conclusion

The inverted repeating number triangle pattern is a small nested-loop exercise with lasting payoff: row/column thinking, print(..., end="") vs print(), and O(n²) intuition. Master the classic two-loop version, then optionally shorten rows with str(i) * i.

Practice the three examples above, then continue to Program 12 for the next pattern in the series.

Row i repeats digit i — keep print(i, end="") for each copy and print() for the break, and validate row counts when reading input.

View Examples Gallery Continue to Program 12

Pro Tips

💡 Best Practices

✅ Do

Explain outer picks digit, inner counts repeats before coding
Use print(i, end="") for repeats and print() after each row
Validate rows ≥ 1 for interactive programs
Wrap int(input()) in try/except ValueError before using rows
State O(n²) time when asked about complexity

❌ Don’t

Call print() inside the inner repeat loop
Use for j in range(rows, i - 1, -1) when you meant Program 10 instead
Skip the newline after each row
Ignore bad console input in user-facing demos
Skip the rows = 1 edge case

Summary

Key Takeaways

Knowledge Unlocked

Five things to remember about this repeating pattern

Print the triangle the beginner-friendly way.

Core concepts

△ 01

Rule

Row i repeats digit i

Definition

↻ 02

Outer loop

Picks the digit each row

Code

1 03

Inner loop

Repeats digit with print(i, end="")

Code

↵ 04

print()

Ends each row

I/O

O 05

Complexity

O(n²) time

Analysis

❓ Frequently Asked Questions

Why does the number of repeats decrease each row?

The outer loop decreases i from rows down to 1, and the inner loop runs j from 1 to i. Row i repeats digit i exactly i times, so the widest row is first and each next row is shorter.

How does the inner loop repeat digit i exactly i times?

for j in range(1, i + 1): print(i, end="") runs the inner body i times. When i is 5 you get 55555; when i is 1 you get a single 1.

What is the difference between print with end= and print()?

print(i, end="") stays on the same line. print() ends the current line. Repeated digits use end=""; the row break uses print() after the inner loop.

How is this different from Program 10?

Program 10 grows repeat count as the digit shrinks (5, 44, 333, 2222, 11111) using for j in range(rows, i - 1, -1). Program 11 repeats digit i exactly i times (55555, 4444, 333, 22, 1) using for j in range(1, i + 1).

What is the time complexity?

O(n²) where n is the number of rows. Total print calls equal n+(n-1)+…+1 = n(n+1)/2.

Can I use string multiplication instead of an inner loop?

Yes. print(str(i) * i) prints a full row in one call. Nested loops are better for learning; str(i) * i is a handy shortcut once the bounds make sense.

How should I read the row count safely?

Use a try/except ValueError around int(input()) or check the raw string with .isdigit() before converting so bad input does not crash the script.

What happens if rows is 0 or negative?

The outer loop never runs, so nothing is printed. Validate and prompt again if you want a clear user message.

Did you Know? 🔊

Row digit i repeats exactly i times. The outer loop counts down from rows, so the first row is widest (rows copies of rows) and each line shortens — still O(n²) total prints.

Continue to Program 12

Next up — ascending repeating shrinking pattern in the series.

Program 12 tutorial →

About the author

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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Python Number Pattern 10 — Descending Repeating Number Triangle Python Number Pattern 12 — Ascending Repeating Shrinking

Inverted Repeating Number Triangle Pattern in Python

What You’ll Learn

Shape Rule

Outer Loop

Inner Loop

print end= vs print()

Live Preview

O(n²)

Introduction

Why it matters?

Row = Repeat Count

Two Nested Loops

Print Then Break

Series Foundation

📝 Problem & Approach

Inputs & Outputs

Minimal workflow

Approach comparison

⚡ Quick Reference

📋 print end= vs print() vs str(i) *

When This Pattern Shows Up

First lab exercise

Nested-loop warm-up

Console I/O practice

Gateway to variants

Not a UI layout tool

🔮 Live Preview

Examples Gallery

📚 Getting Started

Example 1 — Fixed rows = 5

How It Works

📈 Practical Variant

Example 2 — User Input Version

How It Works

⚡ Shortcut Style

Example 3 — str(i) * i

How It Works

🧠 How the Algorithm Prints Rows

Set up

Outer loop (rows)

Inner loop (repeats)

New line

Triangle complete

🔎 Worked Walkthrough — rows = 4

Use Cases

1. Teaching Nested Loops

2. Pattern Series Base

3. Console Formatting Drills

4. Character Substitution

5. Complexity Intuition

6. Input Validation Labs

Advantages

1. Instant Visual Feedback

2. Minimal Concepts

3. Easy to Extend

4. O(1) Extra Memory

Usage Tips

1. Name Bounds Clearly

2. Prefer try/except ValueError

3. Keep print() Outside

4. Use j <= i for Repeat Count

5. Dry-Run One Small n

Common Pitfalls

1. print() Inside the Inner Loop

2. Wrong Inner Bound

3. Forgetting the Row Break

4. Blind int(input())

5. Off-by-One on 0-Based Loops

Edge Cases

Single repeated digit

Empty pattern

rows < 0

Many rows

Non-numeric input()

Inner bound j <= rows by mistake

🎯 Practice Problems

1. Descending repeating triangle

2. Program 12 follow-up

3. Safe input loop

4. Same digit, different count

Example 1 — Fixed `rows = 5`

Example 3 — `str(i) * i`

🔎 Worked Walkthrough — `rows = 4`

2. Prefer `try/except ValueError`

`rows < 0`