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()