Demo/turtle/tdemo_tree.py

   1 #!/usr/bin/python
   2 """      turtle-example-suite:
   3
   4              tdemo_tree.py
   5
   6 Displays a 'breadth-first-tree' - in contrast
   7 to the classical Logo tree drawing programs,
   8 which use a depth-first-algorithm.
   9
  10 Uses:
  11 (1) a tree-generator, where the drawing is
  12 quasi the side-effect, whereas the generator
  13 always yields None.
  14 (2) Turtle-cloning: At each branching point the
  15 current pen is cloned. So in the end there
  16 are 1024 turtles.
  17 """
  18 from turtle import Turtle, mainloop
  19 from time import clock
  20
  21 def tree(plist, l, a, f):
  22     """ plist is list of pens
  23     l is length of branch
  24     a is half of the angle between 2 branches
  25     f is factor by which branch is shortened
  26     from level to level."""
  27     if l > 3:
  28         lst = []
  29         for p in plist:
  30             p.forward(l)
  31             q = p.clone()
  32             p.left(a)
  33             q.right(a)
  34             lst.append(p)
  35             lst.append(q)
  36         for x in tree(lst, l*f, a, f):
  37             yield None
  38
  39 def maketree():
  40     p = Turtle()
  41     p.setundobuffer(None)
  42     p.hideturtle()
  43     p.speed(0)
  44     p.tracer(30,0)
  45     p.left(90)
  46     p.penup()
  47     p.forward(-210)
  48     p.pendown()
  49     t = tree([p], 200, 65, 0.6375)
  50     for x in t:
  51         pass
  52     print len(p.getscreen().turtles())
  53
  54 def main():
  55     a=clock()
  56     maketree()
  57     b=clock()
  58     return "done: %.2f sec." % (b-a)
  59
  60 if __name__ == "__main__":
  61     msg = main()
  62     print msg
  63     mainloop()