sierpinski generation

sierpinski.py

import turtle
import math

WIDTH, HEIGHT = 800, 600
ANGLE = 60
SCALAR = 1.585
DEPTH = 8


def main():
    wn = turtle.Screen()
    wn.delay(0)
    wn.bgcolor("lightgreen")
    
    cursor = turtle.Turtle()
    cursor.speed(0)
    cursor.penup()
    cursor.pensize(2)
    cursor.setx(-WIDTH // 2)
    cursor.sety(-HEIGHT // 2 - 20)
    cursor.pendown()
    cursor.color("green")
    
    grammar = {"rules": {'A': '+B-A-B+',
                         'B': '-A+B+A-'},
               "variables": ('A', 'B'),
               "constants": ('+', '-')}
   
    print("[------Generic System Plotter------]")
    print("variables: " + str(grammar["variables"]))
    print("constants: " + str(grammar["constants"]))
    print("rules: ")
    for k, v in grammar["rules"].items():
        print("\t {} -> \"{}\"".format(k, v))
    print("depth: " + str(DEPTH))
    
    print("\nGenerating instructions...")

    instructions = generate_sierpinski(DEPTH, 'A', grammar)
    print("Result: \n" + instructions)
    
    DISTANCE = WIDTH / (2 ** DEPTH)
    tasks = {"A": lambda t: t.forward(DISTANCE),
             "B": lambda t: t.forward(DISTANCE),
             "-": lambda t: t.right(ANGLE),
             "+": lambda t: t.left(ANGLE)}
    
    print("\nDrawing instructions...")
    draw_instructions(instructions, tasks, cursor)
    print("\nDONE!")
    wn.mainloop()


def draw_instructions(instructions, tasks, cursor):
    for token in instructions:
        if token in tasks:
            tasks[token](cursor)
        

def generate_sierpinski(depth, token, grammar):
    if depth == 0:
        return token
    
    if token in grammar["constants"]:
        return token
    
    if token in grammar["variables"]:
        rule = grammar["rules"][token]
        expression = ''
        for character in rule:
            expression += generate_sierpinski(depth - 1, character, grammar)
        return expression
    

if __name__ == "__main__":
    main()