Python Implementation of Producer-Consumer Solution using Semaphore














































Python Implementation of Producer-Consumer Solution using Semaphore



Implementation of Producer-Consumer Solution using Semaphore

Description: The producer-consumer problem arises when a process is producing some data, the producer, and another process is using that data, the consumer. The producer and the consumer, however, could be operating at different rates, ie the consumer could be using data quicker than the producer can produce it. To support this we need to offer a queue structure for the producer to place data onto and the consumer to take from and also a count of how many items exist on the queue, so producers cannot place too much data on the queue and consumers do not try and take data that is not there.


Since producers and consumers are running at the same time we will use thread. For this, we will import Semaphore, Thread from threading module in Python.  

Program:

from threading import Thread, Semaphore
import time
import random

queue = [] #queue from where producer will produce data and consumer will
consume data
MAX_NUM = 10 #max limit of the queue

sem = Semaphore() #intitializing semaphore

class ProducerThread(Thread):
def run(self):
nums = range(5) # [0 1 2 3 4]
global queue
while True:
sem.acquire() #wait operation to stop consuming
if len(queue) == MAX_NUM:
print ("List is full, producer will wait")
sem.release() #signal operation only when when queue is full and
allow consumer to consume data
print ("Space in queue, Consumer notified the producer")

num = random.choice(nums)
queue.append(num) #added any random number from 0 to 4 to the list
print ("Produced", num)
sem.release() #signal operation to allow consumer to consume data

time.sleep(random.random()) #to allow program to run a bit slower

class ConsumerThread(Thread):
def run(self):
global queue
while True:
sem.acquire() #wait operation to stop producing
if not queue:
print ("List is empty, consumer waiting")
sem.release() #signal operation only when when queue is empty and allow
producer to produce data
print ("Producer added something to queue and notified the consumer")

num = queue.pop(0)
print ("Consumed", num)
sem.release() #signal operation to allow producer to produce

time.sleep(random.random())

def main():
ProducerThread().start() #start producer thread
ConsumerThread().start() #start consumer thread

if __name__ == '__main__':
main()


Output:


Produced 2
Produced 4
Produced 4
Produced 2
Produced 1
Produced 1
Produced 1
Produced 0
Produced 1
Produced 2
List is full, producer will wait Space
Space in queue, Consumer notified the producer Produced
Produced 2
Produced 0
Produced 0
.....
#this will continue untill keyboard interrupt



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