Python Multithreaded Program

 

MULTITHREADED PROGRAMMING

 Multithreading is the ability of a process to execute multiple threads parallelly .

  STARTING A NEW THREAD

MULTITHREADING EXAMPLE.

#PYTHON MULTITHREADING EXAMPLE.

#1. CALCULATE FACTORIAL USING RECURSION.

#2. CALL FACTION USING THREAD.

 

from _thread import start_new_thread

threadld = 1

 

def factorial(n):

     global threadld

     if n < 1:  #base case

          print("%s: %d" % ("Thread",threadld))

          threadld += 1

          return 1

     else:

        returnNumber  = n * factorial( n - 1) # recursive call

        print(str(n) + '! = ' + str(returnNumber))

        return returnNumber

start_new_thread(factorial,(5, ))

start_new_thread(factorial,(4, ))

c = input("waiting for threads to return...\n")

#PYTHON MULTITHREADING: PROGRAM OUTPUT

waiting for threads to return...

Thread: 1

1! = 1

2! = 2

3! = 6

4! = 24

Thread: 2

1! = 1

2! = 2

3! = 6

4! = 24

5! = 120

 

CREATING THREAD USING THREADING MODULE

EXAMPLE

import threading

import time

 

exitFlag = 0

 

class myThread (threading.Thread):

   def __init__(self, threadID, name, counter):

      threading.Thread.__init__(self)

      self.threadID = threadID

      self.name = name

      self.counter = counter

   def run(self):

      print ("Starting " + self.name)

      print_time(self.name, self.counter, 5)

      print ("Exiting " + self.name)

 

def print_time(threadName, delay, counter):

   while counter:

      if exitFlag:

         threadName.exit()

      time.sleep(delay)

      print ("%s: %s" % (threadName, time.ctime(time.time())))

      counter -= 1

 

# Create new threads

thread1 = myThread(1, "Thread-1", 1)

thread2 = myThread(2, "Thread-2", 2)

 

# Start new Threads

thread1.start()

thread2.start()

 

print ("Exiting Main Thread")

WHEN THE ABOVE CODE IS EXECUTED, IT PRODUCES THE FOLLOWING RESULT

>>>

Starting Thread-1Starting Thread-2Exiting Main Thread

 

 

>>> Thread-1: Fri Jun 23 17:54:55 2023

Thread-2: Fri Jun 23 17:54:56 2023

Thread-1: Fri Jun 23 17:54:56 2023

Thread-1: Fri Jun 23 17:54:57 2023

Thread-2: Fri Jun 23 17:54:58 2023Thread-1: Fri Jun 23 17:54:58 2023

 

Thread-1: Fri Jun 23 17:54:59 2023

Exiting Thread-1

Thread-2: Fri Jun 23 17:55:00 2023

Thread-2: Fri Jun 23 17:55:02 2023

Thread-2: Fri Jun 23 17:55:04 2023

Exiting Thread-2

SYNCHRONIZING THREADS:

import threading

import time

 

class myThread (threading.Thread):

   def __init__(self, threadID, name, counter):

      threading.Thread.__init__(self)

      self.threadID = threadID

      self.name = name

      self.counter = counter

   def run(self):

      print ("Starting " + self.name)

      # Get lock to synchronize threads

      threadLock.acquire()

      print_time(self.name, self.counter, 3)

      # Free lock to release next thread

      threadLock.release()

 

def print_time(threadName, delay, counter):

   while counter:

      time.sleep(delay)

      print ("%s: %s" % (threadName, time.ctime(time.time())))

      counter -= 1

 

threadLock = threading.Lock()

threads = []

 

# Create new threads

thread1 = myThread(1, "Thread-1", 1)

thread2 = myThread(2, "Thread-2", 2)

 

# Start new Threads

thread1.start()

thread2.start()

 

# Add threads to thread list

threads.append(thread1)

threads.append(thread2)

 

# Wait for all threads to complete

for t in threads:

   t.join()

print ("Exiting Main Thread")

Output

>>>

Starting Thread-1Starting Thread-2

 

Thread-1: Fri Jun 23 17:57:28 2023

Thread-1: Fri Jun 23 17:57:29 2023

Thread-1: Fri Jun 23 17:57:30 2023

Thread-2: Fri Jun 23 17:57:32 2023

Thread-2: Fri Jun 23 17:57:34 2023

Thread-2: Fri Jun 23 17:57:36 2023

Exiting Main Thread

MULTITHREAD  PRIORITY QUEUE

import queue

import threading

import time

 

exitFlag = 0

 

class myThread (threading.Thread):

   def __init__(self, threadID, name, q):

      threading.Thread.__init__(self)

      self.threadID = threadID

      self.name = name

      self.q = q

   def run(self):

      print ("Starting " + self.name)

      process_data(self.name, self.q)

      print ("Exiting " + self.name)

 

def process_data(threadName, q):

   while not exitFlag:

      queueLock.acquire()

      if not workQueue.empty():

         data = q.get()

         queueLock.release()

         print ("%s processing %s" % (threadName, data))

      else:

         queueLock.release()

         time.sleep(1)

 

threadList = ["Thread-1", "Thread-2", "Thread-3"]

nameList = ["One", "Two", "Three", "Four", "Five"]

queueLock = threading.Lock()

workQueue = queue.Queue(10)

threads = []

threadID = 1

 

# Create new threads

for tName in threadList:

   thread = myThread(threadID, tName, workQueue)

   thread.start()

   threads.append(thread)

   threadID += 1

 

# Fill the queue

queueLock.acquire()

for word in nameList:

   workQueue.put(word)

queueLock.release()

 

# Wait for queue to empty

while not workQueue.empty():

   pass

 

# Notify threads it's time to exit

exitFlag = 1

 

# Wait for all threads to complete

for t in threads:

   t.join()

print ("Exiting Main Thread")

Output

>>>

Starting Thread-2Starting Thread-1

 

Starting Thread-3Thread-1 processing OneThread-2 processing Two

 

 

Thread-3 processing ThreeThread-1 processing FourThread-2 processing Five

 

 

Exiting Thread-3Exiting Thread-1Exiting Thread-2

 

 

Exiting Main Thread

>>>