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1 #!/usr/bin/env python3
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2 """ turtle-example-suite:
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3
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4 xtx_lindenmayer_indian.py
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5
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6 Each morning women in Tamil Nadu, in southern
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7 India, place designs, created by using rice
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8 flour and known as kolam on the thresholds of
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9 their homes.
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10
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11 These can be described by Lindenmayer systems,
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12 which can easily be implemented with turtle
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13 graphics and Python.
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14
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15 Two examples are shown here:
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16 (1) the snake kolam
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17 (2) anklets of Krishna
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18
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19 Taken from Marcia Ascher: Mathematics
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20 Elsewhere, An Exploration of Ideas Across
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21 Cultures
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22
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23 """
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24 ################################
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25 # Mini Lindenmayer tool
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26 ###############################
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27
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28 from turtle import *
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29
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30 def replace( seq, replacementRules, n ):
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31 for i in range(n):
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32 newseq = ""
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33 for element in seq:
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34 newseq = newseq + replacementRules.get(element,element)
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35 seq = newseq
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36 return seq
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37
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38 def draw( commands, rules ):
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39 for b in commands:
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40 try:
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41 rules[b]()
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42 except TypeError:
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43 try:
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44 draw(rules[b], rules)
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45 except:
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46 pass
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47
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48
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49 def main():
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50 ################################
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51 # Example 1: Snake kolam
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52 ################################
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53
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54
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55 def r():
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56 right(45)
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57
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58 def l():
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59 left(45)
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60
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61 def f():
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62 forward(7.5)
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63
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64 snake_rules = {"-":r, "+":l, "f":f, "b":"f+f+f--f--f+f+f"}
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65 snake_replacementRules = {"b": "b+f+b--f--b+f+b"}
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66 snake_start = "b--f--b--f"
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67
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68 drawing = replace(snake_start, snake_replacementRules, 3)
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69
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70 reset()
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71 speed(3)
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72 tracer(1,0)
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73 ht()
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74 up()
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75 backward(195)
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76 down()
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77 draw(drawing, snake_rules)
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78
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79 from time import sleep
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80 sleep(3)
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81
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82 ################################
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83 # Example 2: Anklets of Krishna
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84 ################################
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85
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86 def A():
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87 color("red")
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88 circle(10,90)
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89
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90 def B():
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91 from math import sqrt
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92 color("black")
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93 l = 5/sqrt(2)
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94 forward(l)
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95 circle(l, 270)
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96 forward(l)
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97
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98 def F():
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99 color("green")
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100 forward(10)
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101
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102 krishna_rules = {"a":A, "b":B, "f":F}
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103 krishna_replacementRules = {"a" : "afbfa", "b" : "afbfbfbfa" }
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104 krishna_start = "fbfbfbfb"
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105
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106 reset()
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107 speed(0)
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108 tracer(3,0)
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109 ht()
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110 left(45)
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111 drawing = replace(krishna_start, krishna_replacementRules, 3)
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112 draw(drawing, krishna_rules)
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113 tracer(1)
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114 return "Done!"
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115
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116 if __name__=='__main__':
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117 msg = main()
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118 print(msg)
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119 mainloop()
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