Nested loops: print pattern - triangle of stars

Problem: Print the following pattern for a given n (e.g. n=5 below).

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

Solution in Python:

def print_pattern(n):

    """

    n is number of colmns or rows.

    """

    for i in range(n):
        s = ""

        for j in range(i+1):
            s += "*"

        print s

Concepts learned: nested loops.