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#!/usr/bin/env python3
""" turtle-example-suite:
tdemo_tree.py
Displays a 'breadth-first-tree' - in contrast
to the classical Logo tree drawing programs,
which use a depth-first-algorithm.
Uses:
(1) a tree-generator, where the drawing is
quasi the side-effect, whereas the generator
always yields None.
(2) Turtle-cloning: At each branching point
the current pen is cloned. So in the end
there are 1024 turtles.
"""
from turtle import Turtle, mainloop
from time import perf_counter as clock
def tree(plist, l, a, f):
""" plist is list of pens
l is length of branch
a is half of the angle between 2 branches
f is factor by which branch is shortened
from level to level."""
if l > 3:
lst = []
for p in plist:
p.forward(l)
q = p.clone()
p.left(a)
q.right(a)
lst.append(p)
lst.append(q)
for x in tree(lst, l*f, a, f):
yield None
def maketree():
p = Turtle()
p.setundobuffer(None)
p.hideturtle()
p.speed(0)
p.getscreen().tracer(30,0)
p.left(90)
p.penup()
p.forward(-210)
p.pendown()
t = tree([p], 200, 65, 0.6375)
for x in t:
pass
def main():
a=clock()
maketree()
b=clock()
return "done: %.2f sec." % (b-a)
if __name__ == "__main__":
msg = main()
print(msg)
mainloop()
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