Repeating Number Triangle in Python

Beginner

⏱️ 8 min read

📚 Updated: Sep 2026

🎯 3 Code Examples

🚀 Live Preview

Nested Loops

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

Overview

What You’ll Learn

Program 9 prints a repeating number triangle: each row repeats the row digit i exactly i times — 1, 22, 333, and so on. This tutorial covers the shape rule, outer loop for the digit, inner loop for repetition, a live preview, worked Python examples, edge cases, and complexity.

Shape Rule

Repeat i, i times

Row with outer i = 3 prints 333 — the digit equals the row number, repeated that many times.

Outer Loop

i = 1..rows

for i in range(1, rows + 1) — chooses which digit to repeat on each row.

Inner Loop

j = 1..i

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

print vs newline

Same line / next line

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

Live Preview

rows = 3..9

Pick row count and draw the repeating triangle in the browser.

O(n²)

Complexity

Total prints = 1+2+…+n = n(n+1)/2 — a triangular number.

Introduction

A repeating number triangle prints the row digit multiple times: row 1 prints 1 once, row 2 prints 2 twice, row 3 prints 3 three times, and so on. With rows = 5, you get 1, 22, 333, 4444, 55555.

In Python use an outer loop from 1 to rows, an inner loop that runs i times printing i each time, then print() after each row.

Why it matters?

It teaches that the inner loop controls repetition count while the outer loop picks the value — a stepping stone to repeating stars and alphabets.

Key Highlights

Outer picks digit

i is both row number and print value.

Inner repeats

Inner runs i times, prints i.

vs Program 8

Program 8 prints descending sequences; Program 9 repeats one digit.

Series Step

Follow Program 8; continue to Program 10 next.

In short: outer i = 1..rows, inner j = 1..i, print(i, end="") each time, then print().

Foundation

📝 Problem & Approach

Given row count rows = 5, print a repeating number triangle — row i shows digit i repeated i times.

Python

# rows = 5
# 1
# 22
# 333
# 4444
# 55555

Inputs & Outputs

Item	Type	Description
`rows`	int	Triangle height — also the widest row digit count.
`i` (outer)	int	Current row digit — runs `1` up to `rows`.
`j` (inner)	int	Repetition counter — runs `1..i`, prints `i` each time.
Row width	int	Row with outer `i` prints exactly `i` copies of digit `i`.
First row	int	Single digit `1` when `i = 1`.
Last row	string	Digit `rows` repeated `rows` times.

Minimal workflow

Pseudocode

for i from 1 to rows:
    repeat i times:
        print i
    print newline

Approach comparison

Approach	Idea	Best for
Nested loops	`for j = 1..i` print `i`	Standard teaching approach
Descending outer	`for i in range(rows, 0, -1)`	Mirror triangle variant
User-input rows	`int(input())`	Flexible height
Compact trace	`rows = 3` on paper first	Quick dry-runs
Spaced output	`print(i, end=" ")`	Readable columns

Cheat Sheet

⚡ Quick Reference

Goal	Pattern
Outer loop	`for i in range(1, rows + 1)`
Inner loop	`for j in range(1, i + 1): print(i, end="")`
End row	`print()`
Program 5 contrast	Program 5: print j (1..i); Program 9: print i (repeat i times)

Compare

📋 Fixed Rows vs User Input vs Compact Trace

Same repeating triangle — three ways to set row count and trace the logic.

Fixed rows

rows = 5

Hard-coded height for demos

User input

int(input())

Read row count from console

Compact trace

rows = 3

Quick dry-run on paper

Outer

i = 1..rows

Chooses digit to repeat

Inner

j = 1..i

Repetition count

Context

When This Pattern Shows Up

Reach for this pattern when teaching inner-loop repetition and comparing print value vs loop counter.

Post Program 8 exercise
Simpler than descending sequences — one digit repeated per row builds repetition intuition.
Gateway to star patterns
Same inner-loop repetition idea extends to repeating * or letters.
Interview warm-ups
Classic nested-loop question — explain outer picks value, inner controls count.
Gateway to Program 10
Compare this ascending repeat with the descending repeat in Program 10.
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 value-vs-counter thinking and O(n²) repetition.

Interactive

🔮 Live Preview

Choose a row count between 3 and 9 and draw the repeating number triangle in the browser.

Hands-On

Examples Gallery

Three complete Python programs — fixed rows, user input, and a compact trace with rows = 3. Click View Output to reveal sample console results.

📚 Getting Started

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

How It Works

Outer i runs 1 to 5 — inner j runs 1 to i, printing i each time.

📈 Practical Variant

Read row count from the user with validation.

Example 2 — User Input Rows

Configurable height with int(input()) and a positive-rows check.

Python

try:
    rows = int(input("Enter the number of rows: "))
    if rows <= 0:
        raise ValueError
except ValueError:
    print("Please enter a positive integer.")
else:
    for i in range(1, rows + 1):
        for j in range(1, i + 1):
            print(i, end="")
        print()

How It Works

Same nested loops — only the row count comes from console input with safe parsing.

⚡ Compact Trace

Use rows = 3 for a quick paper trace before larger triangles.

Example 3 — Compact `rows = 3` Trace

Small triangle — easy to dry-run on paper before scaling up.

Python

rows = 3

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

How It Works

Three rows, six total digits — trace i and inner count on paper before coding rows = 5.

🧠 How the Nested Loops Build Each Row

Choose the row count

rows = 5 sets how many rows to print.

Setup

Outer loop (choose digit)

for i in range(1, rows + 1) picks which digit to repeat on each row.

Row control

Inner loop (repeat i times)

for j in range(1, i + 1) prints i exactly i times per row.

Repeat digit

New line

print() moves to the next row after each line is printed.

Line break

Repeating triangle complete

Total printed digits follow triangular numbers: n(n+1)/2, so time complexity is O(n²).

Trace

🔎 Worked Walkthrough — `rows = 5`

Trace each row — outer i is the digit, inner j counts repetitions from 1 to i.

Row (i)	Inner runs	Output line
1	1 time	`1`
2	2 times	`22`
3	3 times	`333`
4	4 times	`4444`
5	5 times	`55555`

Total digits printed: 1+2+3+4+5 = 15 = 5×6/2 — the fifth triangular number.

Use Cases

Where this repetition pattern shows up beyond the homework prompt.

1. Teaching Repetition

Inner loop count equals print value — clearest introduction to repeat-N-times logic.

Example: trace row 3 and watch i print three times.

2. Pair with Program 8

Program 8 prints descending sequences; Program 9 repeats one digit — same O(n²) total.

Example: compare output side by side for rows = 5.

3. Gateway to Star Patterns

Same inner-loop repetition extends to printing * or letters per row.

Example: replace print(i, end="") with print("*", end="").

4. Compare with Program 5

Same inner bound 1..i — Program 5 prints j, Program 9 prints i.

Example: swap print value and see 123 vs 111 on row 3.

5. Complexity Intuition

Triangular totals make O(n²) concrete for beginners.

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

6. Input Validation Labs

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

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

Pro Tip: when an interviewer asks for patterns, explain outer picks value and inner controls count first — then write the loops.

Advantages

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

1. Simplest Repetition Pattern
One digit repeated — wrong print value shows up immediately.
2. Minimal Concepts
Only loops and console output — no arrays or math libraries.
3. Easy to Extend
Swap digits for stars, letters, or spaced output with one-line edits.
4. O(1) Extra Memory
Streaming output needs no storage beyond loop counters.

Pro Tip: trace rows = 3 on paper — row 2 should print exactly two twos.

Usage Tips

Small habits that keep repeating-triangle code clean.

1. Print i, Not j
print(i, end="") repeats the row digit — printing j gives 123 instead of 333.
2. Use try/except for input
Wrap int(input()) in try/except ValueError when the user might type letters.
3. Keep Newline Outside
Only call print() after the inner loop finishes the row.
4. Inner Bound Is 1..i
for j in range(1, i + 1) — row i gets exactly i prints.
5. Dry-Run One Small n
Trace rows = 3 on paper before coding larger demos.

Pro Tip: if row 3 shows 123 instead of 333, you are printing j instead of i.

Common Pitfalls

Mistakes that commonly break repeating number triangles.

1. Printing j Instead of i
Row 3 prints 123 instead of 333 — classic value-vs-counter mix-up.
→ Use print(i, end="") inside the inner loop.
2. Forgetting Newline After Each Row
All digits print on one long line.
→ Call print() after the inner loop.
3. Wrong Inner Bound
Inner running to rows instead of i over-prints each row.
→ Inner loop must be j = 1..i, not 1..rows.
4. Bare int(input())
Letters or empty input raise ValueError when int(input()) is unchecked.
→ Use try/except ValueError and re-prompt on failure.
5. Newline Inside Inner Loop
Each digit prints on its own line — vertical output instead of a triangle.
→ Use print(i, end="") inside, print() outside only.

Edge Cases

Check these inputs before calling the solution done.

rows = 1

Single row

Prints only 1 — inner loop runs once.

rows = 0

Zero rows

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

rows = 2

Minimal triangle

Output 1 then 22 — good quick test.

Negative

Negative rows

Reject with validation before the loops.

Bad input

Non-numeric input

Bare int(input()) raises ValueError — use try/except.

Large n

Many rows

Still O(n²) prints — cap rows for console demos.

Drill

🎯 Practice Problems

Try these variations to lock in the pattern.

1. Compare with Program 5

Program 5: print j (1..i)
Program 9: print i (repeat i times)

2. Repeat stars instead

Replace print(i, end="") with print("*", end="")
Same loops, star triangle

3. Next in series

Continue with Program 10
Descending repeating triangle

4. Paper trace

Dry-run rows = 3 before coding
Fill the walkthrough table by hand

Important

Notes

Row width. Row i prints digit i exactly i times.
Total digits = n(n+1)/2 — triangular number. For rows = 5, that is 15 digits.
Program 5 and Program 9 share inner bound 1..i — only the print value differs.
This pattern extends directly to repeating stars and alphabets in star-pattern programs.

Quick Takeaway: outer i = 1..rows, inner j = 1..i, print(i, end=""), then print().

Analysis

⏱️ Time and Space Complexity

Program	Time	Extra space
Nested loops (Examples 1–2)	`O(rows²)`	`O(1)`
Compact trace (Example 3)	`O(rows²)`	`O(1)`

Wrap Up

🎉 Conclusion

The repeating number triangle is one of the simplest nested-loop exercises: outer picks the digit, inner controls how many times it prints. Master the fixed rows = 5 version, then try user input and the compact rows = 3 trace.

Practice the three examples above, then continue to Program 10 for the descending repeating variant.

Print i not j, keep print() outside the inner loop, and validate row count when reading from the console.

View Examples Gallery Continue to Program 10

Pro Tips

💡 Best Practices

✅ Do

Explain print-i-not-j before coding
Use for j in range(1, i + 1): print(i, end="")
Call print() after each inner loop
Validate rows > 0 for user input
Dry-run rows = 3 on paper first
State O(n²) time when asked about complexity

❌ Don’t

Print j when the pattern needs i
Set inner bound to rows instead of i
Put print() inside the inner loop
Skip input validation on console reads
Confuse this with Program 8’s descending sequence

Summary

Key Takeaways

Knowledge Unlocked

Five things to remember about this repeating pattern

Print the repeating number triangle the beginner-friendly way.

Core concepts

△01

Rule

Repeat i, i times

Definition

↑02

Outer

i = 1..rows

Loop

i03

Print

print(i, end="") not j

Value

#04

Inner

j = 1..i count

Repeat

O05

Complexity

O(n²) time

Analysis

❓ Frequently Asked Questions

What does Number Pattern 9 print?

It prints a repeating number triangle: row 1 shows 1, row 2 shows 22, row 3 shows 333, and so on until row n shows the digit n repeated n times.

Why does each row repeat the same digit?

The inner loop prints the current row number i each time it runs. The inner loop runs i times, so i is repeated i times on that row.

Why does row 4 print 4444?

When i = 4, the inner loop runs 4 times and prints 4 each time — giving 4444 on that line.

How is this different from Program 8?

Program 8 prints descending digits rows..i (5, 54, 543). Program 9 repeats the row digit i times (1, 22, 333).

How is this different from Program 5?

Program 5 prints 1..i ascending per row. Program 9 prints i repeated i times — same inner bound, different print value.

What is the difference between print with and without end?

print(i, end="") stays on the same line for each digit. print() ends the row after the inner loop finishes.

How can I change the number of rows?

Change rows or read it from user input with int(input()) — see Example 2.

Can I print the triangle in descending order?

Yes — make the outer loop count down from rows to 1 while keeping inner 1..i to reduce repeats each row.

What is the time complexity?

O(n²) for n rows because total prints are 1 + 2 + ... + n = n(n+1)/2.

How should I read rows safely?

Use try/except ValueError around int(input()). Bare int(input()) raises ValueError on bad input.

Did you Know? 🔊

Each row repeats the row number i exactly i times — outer i runs 1..rows, inner j prints i on every iteration — producing 1, 22, 333, and so on. Total prints grow as O(n²).

Continue to Program 10

Move on to the descending repeating triangle in the Python number-pattern series.

Program 10 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 8 — Reverse Left-Growing Number Triangle Python Number Pattern 10

Repeating Number Triangle in Python

What You’ll Learn

Shape Rule

Outer Loop

Inner Loop

print vs newline

Live Preview

O(n²)

Introduction

Why it matters?

Outer picks digit

Inner repeats

vs Program 8

Series Step

📝 Problem & Approach

Inputs & Outputs

Minimal workflow

Approach comparison

⚡ Quick Reference

📋 Fixed Rows vs User Input vs Compact Trace

When This Pattern Shows Up

Post Program 8 exercise

Gateway to star patterns

Interview warm-ups

Gateway to Program 10

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 Rows

How It Works

⚡ Compact Trace

Example 3 — Compact rows = 3 Trace

How It Works

🧠 How the Nested Loops Build Each Row

Choose the row count

Outer loop (choose digit)

Inner loop (repeat i times)

New line

Repeating triangle complete

🔎 Worked Walkthrough — rows = 5

Use Cases

1. Teaching Repetition

2. Pair with Program 8

3. Gateway to Star Patterns

4. Compare with Program 5

5. Complexity Intuition

6. Input Validation Labs

Advantages

1. Simplest Repetition Pattern

2. Minimal Concepts

3. Easy to Extend

4. O(1) Extra Memory

Usage Tips

1. Print i, Not j

2. Use try/except for input

3. Keep Newline Outside

4. Inner Bound Is 1..i

5. Dry-Run One Small n

Common Pitfalls

1. Printing j Instead of i

2. Forgetting Newline After Each Row

3. Wrong Inner Bound

4. Bare int(input())

5. Newline Inside Inner Loop

Edge Cases

Single row

Zero rows

Minimal triangle

Negative rows

Non-numeric input

Many rows

🎯 Practice Problems

1. Compare with Program 5

2. Repeat stars instead

3. Next in series

4. Paper trace

Example 1 — Fixed `rows = 5`

Example 3 — Compact `rows = 3` Trace

🔎 Worked Walkthrough — `rows = 5`