Demo/threads/Generator.py

   1 # Generator implementation using threads
   2
   3 import sys
   4 import thread
   5
   6 class Killed(Exception):
   7     pass
   8
   9 class Generator:
  10     # Constructor
  11     def __init__(self, func, args):
  12         self.getlock = thread.allocate_lock()
  13         self.putlock = thread.allocate_lock()
  14         self.getlock.acquire()
  15         self.putlock.acquire()
  16         self.func = func
  17         self.args = args
  18         self.done = 0
  19         self.killed = 0
  20         thread.start_new_thread(self._start, ())
  21
  22     # Internal routine
  23     def _start(self):
  24         try:
  25             self.putlock.acquire()
  26             if not self.killed:
  27                 try:
  28                     apply(self.func, (self,) + self.args)
  29                 except Killed:
  30                     pass
  31         finally:
  32             if not self.killed:
  33                 self.done = 1
  34                 self.getlock.release()
  35
  36     # Called by producer for each value; raise Killed if no more needed
  37     def put(self, value):
  38         if self.killed:
  39             raise TypeError, 'put() called on killed generator'
  40         self.value = value
  41         self.getlock.release()  # Resume consumer thread
  42         self.putlock.acquire()  # Wait for next get() call
  43         if self.killed:
  44             raise Killed
  45
  46     # Called by producer to get next value; raise EOFError if no more
  47     def get(self):
  48         if self.killed:
  49             raise TypeError, 'get() called on killed generator'
  50         self.putlock.release()  # Resume producer thread
  51         self.getlock.acquire()  # Wait for value to appear
  52         if self.done:
  53             raise EOFError  # Say there are no more values
  54         return self.value
  55
  56     # Called by consumer if no more values wanted
  57     def kill(self):
  58         if self.killed:
  59             raise TypeError, 'kill() called on killed generator'
  60         self.killed = 1
  61         self.putlock.release()
  62
  63     # Clone constructor
  64     def clone(self):
  65         return Generator(self.func, self.args)
  66
  67 def pi(g):
  68     k, a, b, a1, b1 = 2L, 4L, 1L, 12L, 4L
  69     while 1:
  70         # Next approximation
  71         p, q, k = k*k, 2L*k+1L, k+1L
  72         a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
  73         # Print common digits
  74         d, d1 = a//b, a1//b1
  75         while d == d1:
  76             g.put(int(d))
  77             a, a1 = 10L*(a%b), 10L*(a1%b1)
  78             d, d1 = a//b, a1//b1
  79
  80 def test():
  81     g = Generator(pi, ())
  82     g.kill()
  83     g = Generator(pi, ())
  84     for i in range(10): print g.get(),
  85     print
  86     h = g.clone()
  87     g.kill()
  88     while 1:
  89         print h.get(),
  90         sys.stdout.flush()
  91
  92 test()