Shrinking Repeating Number Pattern in Python

Beginner

⏱️ 8 min read

📚 Updated: Aug 2026

🎯 3 Code Examples

🚀 Live Preview

Nested Loops

Shrinking repeating number pattern output (11111, 2222, 333, 44, 5) in Python programming

Overview

What You’ll Learn

The shrinking repeating number pattern teaches how a changing inner-loop start value controls row width. 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 rows − i + 1 times

Row 1 prints 11111, row 2 prints 2222, and so on until the last row prints a single digit.

Outer Loop

Rows

for i in range(1, rows + 1): walks each line as the digit increases from 1 to rows.

Inner Loop

Digits

for j in range(i, rows + 1): prints digit i exactly rows − i + 1 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 shrinking repeating number pattern instantly in the browser.

O(n²)

Complexity

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

Introduction

A shrinking repeating number pattern repeats the row digit on each line, but the row becomes shorter as i increases. With rows = 5, the output is 11111, 2222, 333, 44, 5.

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

Why it matters?

It is a great follow-up after growing and inverted repeating patterns. Once you see how the inner-loop start controls width, many number triangles become predictable.

Key Highlights

Row = Repeat Count

On row i, print digit i exactly rows − i + 1 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

Compare Program 9 (growing repeats) and Program 11 (inverted triangle).

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

Foundation

📝 Problem & Approach

Given a positive integer rows, print a shrinking repeating number pattern: row i repeats digit i exactly rows − i + 1 times, with the outer loop counting from 1 up to rows.

Python

# First 5 rows (conceptual shape)
# 11111
# 2222
# 333
# 44
# 5
for i in range(1, rows + 1):
    for j in range(i, rows + 1):
        print(i, end="")   # digit i, repeated (rows - i + 1) 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; row `i` has `rows − i + 1` copies of `i`, so the first row is widest.

Minimal workflow

Pseudocode

for i from 1 to rows:
    for j from i to rows:
        print i (no newline)
    print newline

Approach comparison

Approach	Idea	Best for
Nested loops	Outer digit + inner repeats	Learning and interviews
`str(i) * (rows - i + 1)` 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(1, rows + 1):`
Repeat digit `i`	`for j in range(i, rows + 1): print(i, end="")`
End the row	`print()`
One-line row shortcut	`str(i) * (rows - i + 1)` repeated per row
Program 11 variant	`for j in range(1, i + 1): print(i, end="")` (inverted triangle)

Compare

📋 print end= vs print() vs str(i) *

Same pattern — 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) * (rows - i + 1)

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 pattern when teaching how inner-loop bounds control row width.

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 9 (1, 22, 333, …) and Program 11 (55555, 4444, …) 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 shrinking repeating number pattern 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 shrinking repeating number pattern with nested loops.

Example 1 — Fixed `rows = 5`

Hard-coded height — outer picks digit, inner runs from i to rows.

Python

rows = 5

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

How It Works

When i = 1, the inner loop runs from 1 to 5 and prints 11111. When i = 2, it prints 2222, and so on until i = rows prints a single 5. 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(1, rows + 1):
    for j in range(i, rows + 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) * (rows - i + 1)`

Build each row with str(i) * (rows - i + 1), then print it.

Python

rows = 5

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

How It Works

str(i) * (rows - i + 1) 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(1, rows + 1): picks the digit; the inner loop prints it rows - i + 1 times.

Row

Inner loop (repeats)

for j in range(i, rows + 1): repeats digit i with print(i, end="") as the row shrinks.

Repeats

New line

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

Break

Pattern 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
`1`	`1..4`	4	`1111`
`2`	`2..4`	3	`222`
`3`	`3..4`	2	`33`
`4`	`4..4`	1	`4`

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 for j in range(1, i + 1) and watch the shape change.

2. Pattern Series Base

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

Example: change inner bound to for j in range(1, i + 1) for growing repeats (Program 9).

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) * (rows - i + 1) 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. Start at i, Not 1
for j in range(i, rows + 1): with print(i, end="") is the key to shrinking width.
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 shrinking 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(1, i + 1) grows repeats (1, 22, 333 — Program 9). Using range(1, rows + 1) on every row prints a rectangle.
→ For this shape, keep for j in range(i, rows + 1) so each row shrinks.
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(1, rows + 1) with range(i, rows + 1), or carefully map both values if you go 0-based.

Edge Cases

Check these inputs before calling the solution done.

rows = 1

Single digit

Output is just 1 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 = 1 by mistake

Use j = i so row width shrinks as i grows.

Drill

🎯 Practice Problems

Try these variations to lock in the pattern.

1. Growing repeating pattern

Inner loop j from 1 to i (see Program 9)
Prints 1, 22, 333, …

2. Inverted repeating triangle

Outer loop from rows down to 1
Continue with Program 11

3. Safe input loop

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

4. Spaced output

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 a single 1.
This page is left-aligned. Centered pyramids need leading spaces — covered later in the series.

Quick Takeaway: outer loop picks the digit, inner loop runs from i to rows, 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) * (rows - i + 1)` (Example 3)	`O(rows²)`	`O(rows)` per row string (temporary)

Wrap Up

🎉 Conclusion

The shrinking repeating number pattern is a compact nested-loop exercise: digit increases each row while repeat count shrinks. Master the classic two-loop version, then optionally shorten rows with str(i) * (rows - i + 1).

Practice the three examples above, then continue to Program 13 for the alternating zigzag number triangle.

Row i repeats digit i exactly rows - i + 1 times — keep print(i, end="") for each copy and print() for the break.

View Examples Gallery Continue to Program 13

Pro Tips

💡 Best Practices

✅ Do

Explain outer picks digit, inner start at i 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(1, i + 1) when you meant Program 9 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 shrinking pattern

Print the pattern the beginner-friendly way.

Core concepts

△ 01

Rule

Row i repeats digit i (rows - i + 1) times

Definition

↻ 02

Outer loop

Picks the digit each row

Code

1 03

Inner loop

Runs from i to rows

Code

↵ 04

print()

Ends each row

I/O

O 05

Complexity

O(n²) time

Analysis

❓ Frequently Asked Questions

Why does the row length shrink each time?

The inner loop runs from j = i to rows. As i increases (1, 2, 3, …), the inner loop runs fewer times, so each row prints fewer copies of the row digit.

Why does the first row have five 1s?

On the first row, i = 1 and the inner loop runs from 1 to rows, so it prints 1 exactly rows times — five 1s when rows = 5.

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 do I print 1, 22, 333, … instead?

Use the inner loop as 1..i instead of i..rows so the repeat count grows (see Program 9).

How is this different from Program 11?

Program 11 counts the outer loop down and repeats digit i exactly i times (55555, 4444, 333, 22, 1). Program 12 counts up and uses for j in range(i, rows + 1) so digit i repeats rows - i + 1 times (11111, 2222, 333, 44, 5).

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) * (rows - i + 1)) prints a full row in one call. Nested loops are better for learning; str(i) * count 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 rows − i + 1 times. The outer loop counts up from 1, while the inner loop runs from i to rows, so each row shrinks — still O(n²) total prints.

Continue to Program 13

Next up — alternating ascending/descending rows in Program 13.

Program 13 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 11 — Inverted Repeating Number Triangle Python Number Pattern 13 — Alternating Rows

Shrinking Repeating Number 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) * (rows - i + 1)

How It Works

🧠 How the Algorithm Prints Rows

Set up

Outer loop (rows)

Inner loop (repeats)

New line

Pattern 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. Start at i, Not 1

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 digit

Empty pattern

rows < 0

Many rows

Non-numeric input()

Inner bound j = 1 by mistake

🎯 Practice Problems

1. Growing repeating pattern

2. Inverted repeating triangle

3. Safe input loop

4. Spaced output

Example 1 — Fixed `rows = 5`

Example 3 — `str(i) * (rows - i + 1)`

🔎 Worked Walkthrough — `rows = 4`

2. Prefer `try/except ValueError`

`rows < 0`