CODEWITHSUNDEEP
pythonmultithreadingqueue
DarkSideUser
DarkSideUser

Reputation: 565

Consume queue from other thread

I am developing an script in which I want to have 2 threads. One of them will keep reading serial port and the other one will listen to zmq.

I want to use a queue for the first thread know when to stop reading serial port. so I want the second thread, fill a queue with a character each time it receives a message from zmq.

I already have this:

import serial import struct import threading import sys import zmq from Queue import Queue

  ser = serial.Serial('/dev/ttyUSB0', 38400)
  port = "5556"

  q = Queue(maxsize=0)
  #q = []

  context = zmq.Context()
  socket = context.socket(zmq.SUB)
  socket.connect("tcp://localhost:%s"% port)
  socket.setsockopt(zmq.SUBSCRIBE,'')

  class ReadingThread(threading.Thread):
    def __init__(self):
      super(ReadingThread, self).__init__()
    def run(self):
      while True:
        if q.empty() == False:
            for element in q:
              print element
        data= ser.read()          print "INT", data

  class ZMQThread(threading.Thread):
    def __init__(self):
      super(ZMQThread, self).__init__()
    def run(self):
      while True:
        msg = socket.recv()
        #print "RECIBIDO"
        q.put(msg)

  thread1 = ReadingThread()
  thread1.start()
  thread2 = ZMQThread()
  thread2.start()

But each time the first thread reach the line with q.empty() it crashes:

TypeError: iteration over non-sequence

I also tested with a for element in q: ... but same result.

How can I consume the queue from the first thread?

Upvotes: 0

Views: 195

Answers (1)

yohjp
yohjp

Reputation: 3125

TypeError caused from for element in q: not q.empty(). Because Queue class doesn't provide __iter__() nor __getitem__() methods for for-statement.

You should use get() method to retrieve the element.

Upvotes: 1

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