name : tdemo_lindenmayer_indian.py #! /usr/bin/python2.7 """ turtle-example-suite: xtx_lindenmayer_indian.py Each morning women in Tamil Nadu, in southern India, place designs, created by using rice flour and known as kolam on the thresholds of their homes. These can be described by Lindenmayer systems, which can easily be implemented with turtle graphics and Python. Two examples are shown here: (1) the snake kolam (2) anklets of Krishna Taken from Marcia Ascher: Mathematics Elsewhere, An Exploration of Ideas Across Cultures """ ################################ # Mini Lindenmayer tool ############################### from turtle import * def replace( seq, replacementRules, n ): for i in range(n): newseq = "" for element in seq: newseq = newseq + replacementRules.get(element,element) seq = newseq return seq def draw( commands, rules ): for b in commands: try: rules[b]() except TypeError: try: draw(rules[b], rules) except: pass def main(): ################################ # Example 1: Snake kolam ################################ def r(): right(45) def l(): left(45) def f(): forward(7.5) snake_rules = {"-":r, "+":l, "f":f, "b":"f+f+f--f--f+f+f"} snake_replacementRules = {"b": "b+f+b--f--b+f+b"} snake_start = "b--f--b--f" drawing = replace(snake_start, snake_replacementRules, 3) reset() speed(3) tracer(1,0) ht() up() backward(195) down() draw(drawing, snake_rules) from time import sleep sleep(3) ################################ # Example 2: Anklets of Krishna ################################ def A(): color("red") circle(10,90) def B(): from math import sqrt color("black") l = 5/sqrt(2) forward(l) circle(l, 270) forward(l) def F(): color("green") forward(10) krishna_rules = {"a":A, "b":B, "f":F} krishna_replacementRules = {"a" : "afbfa", "b" : "afbfbfbfa" } krishna_start = "fbfbfbfb" reset() speed(0) tracer(3,0) ht() left(45) drawing = replace(krishna_start, krishna_replacementRules, 3) draw(drawing, krishna_rules) tracer(1) return "Done!" if __name__=='__main__': msg = main() print msg mainloop()