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