Python Program to Print Star Pattern

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

Examples

Inputn = 3

Output* ** ***

Inputn = 5

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

Inputn = 1

Output*

How to Think About It

To print a star pattern, think of each line as having a number of stars equal to the line number. Start from 1 star on the first line, then increase by one star each line until you reach the desired number of lines. Use a loop to repeat this process.

Algorithm

1

Get the number of lines (n) from the user or set it.

2

Start a loop from 1 to n (inclusive).

3

For each number i in the loop, print i stars on that line.

4

Move to the next line and repeat until all lines are printed.

Code

python

n = 5
for i in range(1, n + 1):
    print('*' * i)

Output

*
**
***
****
*****

Dry Run

Let's trace n=3 through the code

1

Set n

n = 3

2

First loop iteration

i = 1, print '*' * 1 -> '*'

3

Second loop iteration

i = 2, print '*' * 2 -> '**'

4

Third loop iteration

i = 3, print '*' * 3 -> '***'

i	Printed Stars
1	*
2	**
3	***

Why This Works

Step 1: Loop controls lines

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

Step 2: Stars printed per line

On each line, '*' * i creates a string with i stars, matching the line number.

Step 3: Print moves to next line

Each print outputs stars and moves to the next line automatically.

Alternative Approaches

Using nested loops

python

n = 5
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, giving more control but more code.

Using while loop

python

n = 5
i = 1
while i <= n:
    print('*' * i)
    i += 1

Uses a while loop instead of for, useful if you prefer while loops.

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

Time Complexity

The outer loop runs n times, and each print creates a string of length up to n, so total work is proportional to n^2.

Space Complexity

Each line creates a string of stars up to length n, so space used per line is O(n).

Which Approach is Fastest?

Using string multiplication is faster and simpler than nested loops because it avoids inner loop overhead.

Approach	Time	Space	Best For
String multiplication	O(n^2)	O(n)	Simple and fast star patterns
Nested loops	O(n^2)	O(1)	More control over printing each star
While loop	O(n^2)	O(n)	Preference for while loops