Using an L-System this draws the Sierpinski Triangle to a given level

L_system.py

import turtle


def run_system(seed, rule, iterations):
    """
    Given the inital seed for the system and the rule function
    run the system for the given number of iterations
    """

    string = seed

    for _ in range(iterations):

        string = "".join(rule(c) for c in string)

    return string


def visualise_system(seed, rule, iterations, visual_rules):

    # Run the system to get the state of the system to viusalise
    string = run_system(seed, rule, iterations)
    print(string)

    # Fire up the turtle
    turtle.st()
    turtle.degrees()
    turtle.home()
    turtle.setheading(0)
    turtle.clear()
    #turtle.tracer(False)

    for c in string:
        visual_rules[c]()

def sierpinski_triangle(iterations):

    def rule(c):
        if c == 'F':
            return 'F-G+F+G-F'
        if c == 'G':
            return 'GG'
        return c

    visual_rules = {'F': lambda: turtle.fd(10),
                    'G': lambda: turtle.fd(10),
                    '+': lambda: turtle.left(120),
                    '-': lambda: turtle.right(120)}

    visualise_system('F-G-G', rule, iterations, visual_rules)

sierpinski_triangle(5)