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      1 """      turtle-example-suite:
      2 
      3          tdemo_round_dance.py
      4 
      5 (Needs version 1.1 of the turtle module that
      6 comes with Python 3.1)
      7 
      8 Dancing turtles have a compound shape
      9 consisting of a series of triangles of
     10 decreasing size.
     11 
     12 Turtles march along a circle while rotating
     13 pairwise in opposite direction, with one
     14 exception. Does that breaking of symmetry
     15 enhance the attractiveness of the example?
     16 
     17 Press any key to stop the animation.
     18 
     19 Technically: demonstrates use of compound
     20 shapes, transformation of shapes as well as
     21 cloning turtles. The animation is
     22 controlled through update().
     23 """
     24 
     25 from turtle import *
     26 
     27 def stop():
     28     global running
     29     running = False
     30 
     31 def main():
     32     global running
     33     clearscreen()
     34     bgcolor("gray10")
     35     tracer(False)
     36     shape("triangle")
     37     f =   0.793402
     38     phi = 9.064678
     39     s = 5
     40     c = 1
     41     # create compound shape
     42     sh = Shape("compound")
     43     for i in range(10):
     44         shapesize(s)
     45         p =get_shapepoly()
     46         s *= f
     47         c *= f
     48         tilt(-phi)
     49         sh.addcomponent(p, (c, 0.25, 1-c), "black")
     50     register_shape("multitri", sh)
     51     # create dancers
     52     shapesize(1)
     53     shape("multitri")
     54     pu()
     55     setpos(0, -200)
     56     dancers = []
     57     for i in range(180):
     58         fd(7)
     59         tilt(-4)
     60         lt(2)
     61         update()
     62         if i % 12 == 0:
     63             dancers.append(clone())
     64     home()
     65     # dance
     66     running = True
     67     onkeypress(stop)
     68     listen()
     69     cs = 1
     70     while running:
     71         ta = -4
     72         for dancer in dancers:
     73             dancer.fd(7)
     74             dancer.lt(2)
     75             dancer.tilt(ta)
     76             ta = -4 if ta > 0 else 2
     77         if cs < 180:
     78             right(4)
     79             shapesize(cs)
     80             cs *= 1.005
     81         update()
     82     return "DONE!"
     83 
     84 if __name__=='__main__':
     85     print(main())
     86     mainloop()
     87