[Python-ideas] channel (synchronous queue)

Sun Feb 19 21:23:03 CET 2012

Den 19.02.2012 20:04, skrev Guido van Rossum:
> Also, writing a performant Channel implementation for multiprocessing 
> would hardly be a trivial job;

I think this should work :-)
Sturla
from multiprocessing import Lock, Event, Pipe
class Channel(object):
 def __init__(self):
 self._writelock = Lock()
 self._readlock = Lock()
 self._new_data = Event()
 self._recv_data = Event()
 self._conn1, self._conn2 = Pipe(False)
 def put(self, msg):
 with self._writelock:
 self._conn2.send(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._conn1.recv()
 self._new_data.clear()
 self._recv_data.set()
 return msg
## -------------
def proc2(channel):
 from sys import stdout
 for i in range(1000):
 msg = channel.get()
 stdout.flush()
 print "Process 2 received '%s'\n" % msg,
 stdout.flush()
def proc1(channel):
 from sys import stdout
 for i in range(1000):
 stdout.flush()
 print "Process 1 preparing to send 'message %d'\n" % i,
 stdout.flush()
 msg = channel.put(("message %d" % i,))
 stdout.flush()
 print "Process 1 finished sending 'message %d'\n" % i,
 stdout.flush()
if __name__ == "__main__":
 from multiprocessing import Process
 channel = Channel()
 p2 = Process(target=proc2, args=(channel,))
 p2.start()
 proc1(channel)
 p2.join()