Python Program to Print Left Triangle Star Pattern

Use a for loop with range(1, n+1) and print stars using print('*' * i) to create a left triangle star pattern in Python.

Examples

Input3

Output* ** ***

Input5

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

Input1

Output*

How to Think About It

To print a left triangle star pattern, think of printing one star on the first line, two stars on the second, and so on until the nth line. Use a loop that counts from 1 to n, and on each iteration, print that many stars.

Algorithm

1

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

2

Start a loop from 1 to n (inclusive).

3

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

4

Move to the next line after printing stars.

5

End the loop after n lines.

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 with input n=3 to see how stars are printed line by line.

1

Input

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 the number of lines

The for loop runs from 1 to n, so it controls how many lines are printed.

Step 2: Stars printed increase each line

On each line, '*' * i prints stars equal to the current line number i.

Step 3: Print moves to next line automatically

The print function adds a new line after printing stars, so each line appears below the previous.

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 lines, inner for stars; slightly longer but shows nested loop concept.

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 understanding different loop types.

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

Time Complexity

The outer loop runs n times, and printing stars takes up to n operations on the last line, so total is roughly O(n^2).

Space Complexity

No extra space is used except loop variables, so space complexity is O(1).

Which Approach is Fastest?

Using '*' * i is concise and efficient; nested loops are more verbose but conceptually clear.

Approach	Time	Space	Best For
Single loop with string multiplication	O(n^2)	O(1)	Simple and concise code
Nested loops	O(n^2)	O(1)	Learning nested loops concept
While loop	O(n^2)	O(1)	Understanding different loop types