Multiprocessing.queues.queue.get

Method Name:

get

Method Signature:

get([block[, timeout]])

Return Value:

NoneType

Parameters:

block

  • A Boolean value specifying whether get() should block till an object is available in the Queue.
  • The default value of this parameter is True.
  • If True, it waits for an object to arrive at the empty Queue by some process.
  • If True while the timeout parameter is specified, then get() blocks for only the number of timeout seconds.
  • If False, it returns immediately upon encountering an empty Queue, raising a queue.Empty exception.

 

timeout

This parameter tells how many seconds to wait, while trying to read from an empty Queue. If the get is not successful till the expiry of timeout seconds, an exception queue.Empty is raised.

 

Method Overview:

  • The method get() reads and removes a Python object from a Queue instance.
  • Once an object is removed from the Queue using get() it is not available in the Queue.
  • Through the parameters block and timeout how long the get() can wait before a successful read of an item from the Queue.

 

Example:

import multiprocessing

import queue

import time

 

QUEUE_LIMIT = 6

 

# Function for consumer process

def consumerFunction(messageQueue):

    count = 0

    while count < QUEUE_LIMIT:

        try:

            count = count + 1

            print("Consumer read:%s"%messageQueue.get(timeout=2))

        except queue.Empty:

            print("Consumer:Timeout reading from the Queue")

   

if __name__ == "__main__":

    multiprocessing.set_start_method = "fork";

   

    messageQueue = multiprocessing.Queue(maxsize=QUEUE_LIMIT)

    consumerProcess = multiprocessing.Process(target=consumerFunction, args=(messageQueue,))

 

    # Start the consumer (Consumer starts first...look at the timeout for get() in consumer function)

    consumerProcess.start()

   

    # Parent process acting as the producer of messages

    for i in range(1, QUEUE_LIMIT+1):

        messageQueue.put("Message%d"%i)

        print("Producer added:Message%d"%i)

        time.sleep(1)

 

    # Wait for the consumer process to complete       

    consumerProcess.join()

 

Output:

Producer added:Message1

Consumer read:Message1

Producer added:Message2

Consumer read:Message2

Producer added:Message3

Consumer read:Message3

Producer added:Message4

Consumer read:Message4

Producer added:Message5

Consumer read:Message5

Producer added:Message6

Consumer read:Message6


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