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1 # Generator implementation using threads
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2
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3 import thread
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4
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5 Killed = 'Generator.Killed'
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6
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7 class Generator:
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8 # Constructor
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9 def __init__(self, func, args):
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10 self.getlock = thread.allocate_lock()
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11 self.putlock = thread.allocate_lock()
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12 self.getlock.acquire()
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13 self.putlock.acquire()
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14 self.func = func
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15 self.args = args
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16 self.done = 0
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17 self.killed = 0
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18 thread.start_new_thread(self._start, ())
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19 # Internal routine
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20 def _start(self):
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21 try:
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22 self.putlock.acquire()
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23 if not self.killed:
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24 try:
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25 apply(self.func, (self,) + self.args)
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26 except Killed:
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27 pass
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28 finally:
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29 if not self.killed:
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30 self.done = 1
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31 self.getlock.release()
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32 # Called by producer for each value; raise Killed if no more needed
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33 def put(self, value):
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34 if self.killed:
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35 raise TypeError, 'put() called on killed generator'
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36 self.value = value
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37 self.getlock.release() # Resume consumer thread
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38 self.putlock.acquire() # Wait for next get() call
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39 if self.killed:
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40 raise Killed
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41 # Called by producer to get next value; raise EOFError if no more
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42 def get(self):
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43 if self.killed:
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44 raise TypeError, 'get() called on killed generator'
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45 self.putlock.release() # Resume producer thread
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46 self.getlock.acquire() # Wait for value to appear
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47 if self.done:
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48 raise EOFError # Say there are no more values
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49 return self.value
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50 # Called by consumer if no more values wanted
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51 def kill(self):
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52 if self.killed:
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53 raise TypeError, 'kill() called on killed generator'
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54 self.killed = 1
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55 self.putlock.release()
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56 # Clone constructor
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57 def clone(self):
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58 return Generator(self.func, self.args)
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59
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60 def pi(g):
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61 k, a, b, a1, b1 = 2L, 4L, 1L, 12L, 4L
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62 while 1:
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63 # Next approximation
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64 p, q, k = k*k, 2L*k+1L, k+1L
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65 a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
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66 # Print common digits
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67 d, d1 = a/b, a1/b1
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68 while d == d1:
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69 g.put(int(d))
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70 a, a1 = 10L*(a%b), 10L*(a1%b1)
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71 d, d1 = a/b, a1/b1
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72
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73 def test():
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74 g = Generator(pi, ())
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75 g.kill()
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76 g = Generator(pi, ())
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77 for i in range(10): print g.get(),
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78 print
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79 h = g.clone()
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80 g.kill()
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81 while 1:
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82 print h.get(),
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83
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84 test()
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