Python Program to Print Right Triangle Pattern

You can print a right triangle pattern in Python using nested loops like for i in range(1, n+1): print('*' * i) where n is the number of rows.

Examples

Input3

Output* ** ***

Input5

Output* ** *** **** *****

Input1

Output*

How to Think About It

To print a right triangle pattern, think of printing one star on the first line, two stars on the second, and so on until the given number of rows. Use a loop that counts from 1 up to the number of rows, and in each step, print that many stars.

Algorithm

1

Get the number of rows (n) from the user or input.

2

Start a loop from 1 to n (inclusive).

3

In each iteration, print stars equal to the current loop number.

4

Move to the next line after printing stars for that row.

Code

python

n = int(input('Enter number of rows: '))
for i in range(1, n + 1):
    print('*' * i)

Output

Enter number of rows: 5
*
**
***
****
*****

Dry Run

Let's trace the program for input 3 to see how it prints the right triangle.

1

Input number of rows

User inputs n = 3

2

First iteration (i=1)

Print '*' repeated 1 time: *

3

Second iteration (i=2)

Print '*' repeated 2 times: **

4

Third iteration (i=3)

Print '*' repeated 3 times: ***

Iteration (i)	Stars Printed
1	*
2	**
3	***

Why This Works

Step 1: Loop controls rows

The for loop runs from 1 to n, controlling how many lines to print.

Step 2: Stars printed per row

In each loop, '*' * i creates a string with i stars, matching the row number.

Step 3: Print moves to next line

Each print outputs stars and moves to the next line automatically, forming the triangle shape.

Alternative Approaches

Using nested loops

python

n = int(input('Enter number of rows: '))
for i in range(1, n + 1):
    for j in range(i):
        print('*', end='')
    print()

This uses two loops: outer for rows, inner for printing stars one by one; slightly longer but shows loop nesting.

Using while loop

python

n = int(input('Enter number of rows: '))
i = 1
while i <= n:
    print('*' * i)
    i += 1

Uses a while loop instead of for loop; good for beginners to understand loop control.

Complexity: O(n^2) time, O(1) space

Time Complexity

The outer loop runs n times, and printing stars takes up to n operations per line, resulting in O(n^2) time.

Space Complexity

The program uses constant extra space, only storing loop counters and printing directly, so O(1) space.

Which Approach is Fastest?

Using string multiplication is faster and simpler than nested loops printing stars one by one.

Approach	Time	Space	Best For
String multiplication	O(n^2)	O(1)	Simple and fast printing
Nested loops	O(n^2)	O(1)	Understanding loop nesting
While loop	O(n^2)	O(1)	Loop control practice