schedutron

import threading

num = 0
lock = Threading.Lock()

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

schedutron

import random, time
from threading import BoundedSemaphore, Thread

max_items = 5
container = BoundedSemaphore(max_items) # consider this as a container with a capacity of 5 items.
                                        # Defaults to 1 if nothing is passed.

def producer(nloops):
   for i in range(nloops):
   time.sleep(random.randrange(2, 5))

schedutron

from threading import Lock, Thread
lock = Lock()
g = 0

def add_one():
   global g # Just used for demonstration. It’s bad to use the ‘global’ statement in general.
   lock.acquire()
   g += 1
   lock.release()