Demo/threads/Generator.py

# Generator implementation using threads

import thread

Killed = 'Generator.Killed'

class Generator:
	# Constructor
	def __init__(self, func, args):
		self.getlock = thread.allocate_lock()
		self.putlock = thread.allocate_lock()
		self.getlock.acquire()
		self.putlock.acquire()
		self.func = func
		self.args = args
		self.done = 0
		self.killed = 0
		thread.start_new_thread(self._start, ())
	# Internal routine
	def _start(self):
		try:
			self.putlock.acquire()
			if not self.killed:
				try:
					apply(self.func, (self,) + self.args)
				except Killed:
					pass
		finally:
			if not self.killed:
				self.done = 1
				self.getlock.release()
	# Called by producer for each value; raise Killed if no more needed
	def put(self, value):
		if self.killed:
			raise TypeError, 'put() called on killed generator'
		self.value = value
		self.getlock.release()	# Resume consumer thread
		self.putlock.acquire()	# Wait for next get() call
		if self.killed:
			raise Killed
	# Called by producer to get next value; raise EOFError if no more
	def get(self):
		if self.killed:
			raise TypeError, 'get() called on killed generator'
		self.putlock.release()	# Resume producer thread
		self.getlock.acquire()	# Wait for value to appear
		if self.done:
			raise EOFError	# Say there are no more values
		return self.value
	# Called by consumer if no more values wanted
	def kill(self):
		if self.killed:
			raise TypeError, 'kill() called on killed generator'
		self.killed = 1
		self.putlock.release()
	# Clone constructor
	def clone(self):
		return Generator(self.func, self.args)

def pi(g):
	k, a, b, a1, b1 = 2L, 4L, 1L, 12L, 4L
	while 1:
		# Next approximation
		p, q, k = k*k, 2L*k+1L, k+1L
		a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
		# Print common digits
		d, d1 = a/b, a1/b1
		while d == d1:
			g.put(int(d))
			a, a1 = 10L*(a%b), 10L*(a1%b1)
			d, d1 = a/b, a1/b1

def test():
	g = Generator(pi, ())
	g.kill()
	g = Generator(pi, ())
	for i in range(10): print g.get(),
	print
	h = g.clone()
	g.kill()
	while 1:
		print h.get(),

test()