#rlock_tut.py
import threading

num = 0
lock = Threading.Lock()

lock.acquire()
num += 1
lock.acquire() # This will block.
num += 2
lock.release()


# With RLock, that problem doesn’t happen.
lock = Threading.RLock()

lock.acquire()
num += 3
lock.acquire() # This won’t block.
num += 4
lock.release()
lock.release() # You need to call release once for each call to acquire.

import random, time
from threading import BoundedSemaphore, Thread
max_items = 5
"""
Consider 'container' as a container, of course, with a capacity of 5
items. Defaults to 1 item if 'max_items' is passed.
"""
container = BoundedSemaphore(max_items)
def producer(nloops):
    for i in range(nloops):
        time.sleep(random.randrange(2, 5))
        print(time.ctime(), end=": ")
        try:
            container.release()
            print("Produced an item.")
        except ValueError:
            print("Full, skipping.")
def consumer(nloops):
    for i in range(nloops):
        time.sleep(random.randrange(2, 5))
        print(time.ctime(), end=": ")
        """
        In the following if statement we disable the default
        blocking behaviour by passing False for the blocking flag.
        """
        if container.acquire(False):
            print("Consumed an item.")
        else:
            print("Empty, skipping.")
threads = []
nloops = random.randrange(3, 6)
print("Starting with %s items." % max_items)
threads.append(Thread(target=producer, args=(nloops,)))
threads.append(Thread(target=consumer, args=(random.randrange(nloops, nloops+max_items+2),)))
for thread in threads:  # Starts all the threads.
    thread.start()
for thread in threads:  # Waits for threads to complete before moving on with the main script.
    thread.join()
print("All done.")

import random, time
from threading import Event, Thread

event = Event()

def waiter(event, nloops):
    for i in range(nloops):
      print(“%s. Waiting for the flag to be set.” % (i+1))
      event.wait() # Blocks until the flag becomes true.
      print(“Wait complete at:”, time.ctime())
      event.clear() # Resets the flag.
      print()

def setter(event, nloops):
    for i in range(nloops):
      time.sleep(random.randrange(2, 5)) # Sleeps for some time.
      event.set()

threads = []
nloops = random.randrange(3, 6)

threads.append(Thread(target=waiter, args=(event, nloops)))
threads[-1].start()
threads.append(Thread(target=setter, args=(event, nloops)))
threads[-1].start()

for thread in threads:
    thread.join()

print(“All done.”)

import random, time
from threading import Condition, Thread
"""
'condition' variable will be used to represent the availability of a produced
item.
"""
condition = Condition()
box = []
def producer(box, nitems):
    for i in range(nitems):
        time.sleep(random.randrange(2, 5))  # Sleeps for some time.
        condition.acquire()
        num = random.randint(1, 10)
        box.append(num)  # Puts an item into box for consumption.
        condition.notify()  # Notifies the consumer about the availability.
        print("Produced:", num)
        condition.release()
def consumer(box, nitems):
    for i in range(nitems):
        condition.acquire()
        condition.wait()  # Blocks until an item is available for consumption.
        print("%s: Acquired: %s" % (time.ctime(), box.pop()))
        condition.release()
threads = []
"""
'nloops' is the number of times an item will be produced and
consumed.
"""
nloops = random.randrange(3, 6)
for func in [producer, consumer]:
    threads.append(Thread(target=func, args=(box, nloops)))
    threads[-1].start()  # Starts the thread.
for thread in threads:
    """Waits for the threads to complete before moving on
       with the main script.
    """
    thread.join()
print("All done.")

from random import randrange
from threading import Barrier, Thread
from time import ctime, sleep

num = 4
# 4 threads will need to pass this barrier to get released.
b = Barrier(num)
names = [“Harsh”, “Lokesh”, “George”, “Iqbal”]

def player():
    name = names.pop()
    sleep(randrange(2, 5))
    print(“%s reached the barrier at: %s” % (name, ctime()))
    b.wait()

threads = []
print(“Race starts now…”)

for i in range(num):
    threads.append(Thread(target=player))
    threads[-1].start()
"""
Following loop enables waiting for the threads to complete before moving on with the main script.
"""
for thread in threads:
    thread.join()
print()
print(“Race over!”)