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()