# Lock
import threading
shared_resource_with_lock = 0
shared_resource_with_no_lock = 0
COUNT = 100000
shared_resource_lock = threading.Lock()
def increment_with_lock():
global shared_resource_with_lock
for i in range(COUNT):
shared_resource_lock.acquire()
shared_resource_with_lock += 1
shared_resource_lock.release()
def decrement_with_lock():
global shared_resource_with_lock
for i in range(COUNT):
shared_resource_lock.acquire()
shared_resource_with_lock -= 1
shared_resource_lock.release()
def increment_without_lock():
global shared_resource_with_no_lock
for i in range(COUNT):
shared_resource_with_no_lock += 1
def decrement_without_lock():
global shared_resource_with_no_lock
for i in range(COUNT):
shared_resource_with_no_lock -= 1
if __name__ == "__main__":
ts=[threading.Thread(target = increment_with_lock),
threading.Thread(target = decrement_with_lock),
threading.Thread(target = increment_without_lock),
threading.Thread(target = decrement_without_lock)]
for t in ts: t.start()
for t in ts: t.join()
print ("the value of shared variable with lock management is %s"%shared_resource_with_lock)
print ("the value of shared variable with race condition is %s"%shared_resource_with_no_lock)
the value of shared variable with lock management is 0
the value of shared variable with race condition is 0
# RLock
import threading
import time
class Box(object):
lock = threading.RLock()
def __init__(self):
self.total_items = 0
def add(self):
Box.lock.acquire()
self.total_items+=1
Box.lock.release()
def remove(self):
Box.lock.acquire()
self.total_items-=1
Box.lock.release()
def adder(box,items):
while items > 0:
print ("adding 1 item in the box\n")
box.add()
time.sleep(3)
items -= 1
def remover(box,items):
while items > 0:
print ("removing 1 item in the box")
box.remove()
time.sleep(1)
items -= 1
if __name__ == "__main__":
items = 5
print ("putting %s items in the box " % items)
box = Box()
ts=[threading.Thread(target=adder,args=(box,items)),
threading.Thread(target=remover,args=(box,items))]
for t in ts: t.start()
for t in ts: t.join()
print ("%s items still remain in the box " % box.total_items)putting 5 items in the box
adding 1 item in the box
removing 1 item in the box
removing 1 item in the box
removing 1 item in the box
adding 1 item in the box
removing 1 item in the box
removing 1 item in the box
adding 1 item in the box
adding 1 item in the box
adding 1 item in the box
0 items still remain in the box
# Queue
from threading import Thread, Event
from queue import Queue
import time
import random
class producer(Thread):
def __init__(self, queue):
Thread.__init__(self)
self.queue = queue
def run(self) :
for i in range(10):
item = random.randint(0, 256)
self.queue.put(item)
print ('Producer notify : item N° %d appended to queue by %s \n' % (item, self.name))
time.sleep(1)
class consumer(Thread):
def __init__(self, queue):
Thread.__init__(self)
self.queue = queue
def run(self):
while True:
item = self.queue.get()
print ('Consumer notify : %d popped from queue by %s' % (item, self.name))
self.queue.task_done()
if __name__ == '__main__':
queue = Queue()
t1 = producer(queue)
t2 = consumer(queue)
t3 = consumer(queue)
t1.start()
t2.start()
t3.start()
t1.join()
t2.join()
t3.join()Producer notify : item N° 249 appended to queue by Thread-1502486
Consumer notify : 249 popped from queue by Thread-1502487
Producer notify : item N° 64 appended to queue by Thread-1502486
Consumer notify : 64 popped from queue by Thread-1502487
Producer notify : item N° 89 appended to queue by Thread-1502486
Consumer notify : 89 popped from queue by Thread-1502488
Producer notify : item N° 160 appended to queue by Thread-1502486
Consumer notify : 160 popped from queue by Thread-1502487
Producer notify : item N° 120 appended to queue by Thread-1502486
Consumer notify : 120 popped from queue by Thread-1502488
Producer notify : item N° 172 appended to queue by Thread-1502486
Consumer notify : 172 popped from queue by Thread-1502487
Producer notify : item N° 158 appended to queue by Thread-1502486
Consumer notify : 158 popped from queue by Thread-1502488
Producer notify : item N° 176 appended to queue by Thread-1502486
Consumer notify : 176 popped from queue by Thread-1502487
Producer notify : item N° 152 appended to queue by Thread-1502486
Consumer notify : 152 popped from queue by Thread-1502488
Producer notify : item N° 210 appended to queue by Thread-1502486
Consumer notify : 210 popped from queue by Thread-1502487
# Semaphore
import threading
import time
import random
# The optional argument init value for the internal counter (defaults to 1)
# If the value given is less than 0, ValueError is raised.
semaphore = threading.Semaphore(0)
def consumer():
print ("consumer is waiting.")
semaphore.acquire()
print ("Consumer notify : consumed item number %s " %item)
def producer():
global item
time.sleep(10)
item = random.randint(0,1000)
print ("producer notify : producted item number %s" %item)
semaphore.release()
if __name__ == '__main__':
for i in range (0,5) :
t1 = threading.Thread(target=producer)
t2 = threading.Thread(target=consumer)
t1.start()
t2.start()
t1.join()
t2.join()
print ("program terminated")consumer is waiting.
producer notify : producted item number 345
Consumer notify : consumed item number 345
consumer is waiting.
producer notify : producted item number 712
Consumer notify : consumed item number 712
consumer is waiting.
producer notify : producted item number 388
Consumer notify : consumed item number 388
consumer is waiting.
producer notify : producted item number 102
Consumer notify : consumed item number 102
consumer is waiting.
producer notify : producted item number 106
Consumer notify : consumed item number 106
program terminated