[Python-ideas] channel (synchronous queue)

Sun Feb 19 17:58:53 CET 2012

Den 19.02.2012 17:01, skrev Antoine Pitrou:
> Even for multiprocessing? (I realize we didn't implement a Barrier in 
> multiprocessing; patches welcome :-)) Regards Antoine. 
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Here is a sceleton (replace self._data with some IPC mechanism for 
multiprocessing).
I'll post a barrier for multiprocessing asap, I happen to have one ;-)
Sturla
from threading import Lock, Event
class Channel(object):
 def __init__(self):
 self._writelock = Lock()
 self._readlock = Lock()
 self._new_data = Event()
 self._recv_data = Event()
 self._data = None
 def put(self, msg):
 with self._writelock:
 self._data = msg
 self._new_data.set()
 self._recv_data.wait()
 self._recv_data.clear()
 def get(self):
 with self._readlock:
 self._new_data.wait()
 msg = self._data
 self._data = None
 self._new_data.clear()
 self._recv_data.set()
 return msg
if __name__ == "__main__":
 from threading import Thread
 from sys import stdout
 def thread2(channel):
 for i in range(1000):
 msg = channel.get()
 stdout.flush()
 print "Thread 2 received '%s'\n" % msg,
 stdout.flush()
 def thread1(channel):
 for i in range(1000):
 stdout.flush()
 print "Thread 1 preparing to send 'message %d'\n" % i,
 stdout.flush()
 msg = channel.put(("message %d" % i,))
 stdout.flush()
 print "Thread 1 finished sending 'message %d'\n" % i,
 stdout.flush()
 channel = Channel()
 t2 = Thread(target=thread2, args=(channel,))
 t2.start()
 thread1(channel)
 t2.join()