Demo/threads/Generator.py

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