multiprocessing.Queue

Overview:

The Queue class in Multiprocessing module of Python Standard Library provides a mechanism to pass data between a parent process and the descendent processes of it.
Multiprocessing.Queues.Queue uses pipes to send data between related ^* processes.

A Pipe is a message passing mechanism between processes in Unix-like operating systems.

For any read/write (get/put method calls) operation the Multiprocessing.Queues.Queue class deserialises/serializes data using Python's pickle module and sends through the underlying pipe.
Python's Multiprocessing.Queues.Queue also uses semaphores and locks to take care of the scenarios involving multiple reader/writer processes.

Example:

import multiprocessing

import time

# Producer/Writer

def procFunction0(messageQueue):

for i in range(1,10):

messageQueue.put("Child1:Message%d"%i)

time.sleep(1)

# Consumer/Reader

def procFunction1(messageQueue):

while messageQueue.empty() is False:

print("From reader:%s"%messageQueue.get())

time.sleep(1)

# Producer/Writer

def procFunction2(messageQueue):

for i in range(1,10):

messageQueue.put("Child3:Message%d"%i)

time.sleep(1)

if __name__ == "__main__":

multiprocessing.set_start_method("fork")

messageQueue = multiprocessing.Queue()

# Create child processes

childProcess0 = multiprocessing.Process(target=procFunction0, args=(messageQueue,))

childProcess1 = multiprocessing.Process(target=procFunction1, args=(messageQueue,))

childProcess2 = multiprocessing.Process(target=procFunction2, args=(messageQueue,))

# Start all the child processes - Writer, Reader, Writer

childProcess0.start()

childProcess1.start()

childProcess2.start()

# Wait for child processes to finish

childProcess0.join()

childProcess1.join()

childProcess2.join()

Output:

From reader:Child1:Message1

From reader:Child3:Message1

From reader:Child1:Message2

From reader:Child3:Message2

From reader:Child1:Message3

From reader:Child3:Message3

From reader:Child1:Message4

From reader:Child3:Message4

From reader:Child3:Message5

From reader:Child1:Message5

From reader:Child1:Message6

From reader:Child3:Message6

From reader:Child1:Message7

From reader:Child3:Message7

From reader:Child1:Message8

From reader:Child3:Message8

From reader:Child3:Message9

From reader:Child1:Message9

Overview:

Example:

Output: