Demo/turtle/tdemo_lindenmayer_indian.py

   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()