1 #!/usr/bin/python

     2 """       turtle-example-suite:

     3 

     4         xtx_lindenmayer_indian.py

     5 

     6 Each morning women in Tamil Nadu, in southern

     7 India, place designs, created by using rice

     8 flour and known as kolam on the thresholds of

     9 their homes.

    10 

    11 These can be described by Lindenmayer systems,

    12 which can easily be implemented with turtle

    13 graphics and Python.

    14 

    15 Two examples are shown here:

    16 (1) the snake kolam

    17 (2) anklets of Krishna

    18 

    19 Taken from Marcia Ascher: Mathematics

    20 Elsewhere, An Exploration of Ideas Across

    21 Cultures

    22 

    23 """

    24 ################################

    25 # Mini Lindenmayer tool

    26 ###############################

    27 

    28 from turtle import *

    29 

    30 def replace( seq, replacementRules, n ):

    31     for i in range(n):

    32         newseq = ""

    33         for element in seq:

    34             newseq = newseq + replacementRules.get(element,element)

    35         seq = newseq

    36     return seq

    37 

    38 def draw( commands, rules ):

    39     for b in commands:

    40         try:

    41             rules[b]()

    42         except TypeError:

    43             try:

    44                 draw(rules[b], rules)

    45             except:

    46                 pass

    47 

    48 

    49 def main():

    50     ################################

    51     # Example 1: Snake kolam

    52     ################################

    53 

    54 

    55     def r():

    56         right(45)

    57 

    58     def l():

    59         left(45)

    60 

    61     def f():

    62         forward(7.5)

    63 

    64     snake_rules = {"-":r, "+":l, "f":f, "b":"f+f+f--f--f+f+f"}

    65     snake_replacementRules = {"b": "b+f+b--f--b+f+b"}

    66     snake_start = "b--f--b--f"

    67 

    68     drawing = replace(snake_start, snake_replacementRules, 3)

    69 

    70     reset()

    71     speed(3)

    72     tracer(1,0)

    73     ht()

    74     up()

    75     backward(195)

    76     down()

    77     draw(drawing, snake_rules)

    78 

    79     from time import sleep

    80     sleep(3)

    81 

    82     ################################

    83     # Example 2: Anklets of Krishna

    84     ################################

    85 

    86     def A():

    87         color("red")

    88         circle(10,90)

    89 

    90     def B():

    91         from math import sqrt

    92         color("black")

    93         l = 5/sqrt(2)

    94         forward(l)

    95         circle(l, 270)

    96         forward(l)

    97 

    98     def F():

    99         color("green")

   100         forward(10)

   101 

   102     krishna_rules = {"a":A, "b":B, "f":F}

   103     krishna_replacementRules = {"a" : "afbfa", "b" : "afbfbfbfa" }

   104     krishna_start = "fbfbfbfb"

   105 

   106     reset()

   107     speed(0)

   108     tracer(3,0)

   109     ht()

   110     left(45)

   111     drawing = replace(krishna_start, krishna_replacementRules, 3)

   112     draw(drawing, krishna_rules)

   113     tracer(1)

   114     return "Done!"

   115 

   116 if __name__=='__main__':

   117     msg = main()

   118     print msg

   119     mainloop()