threading and synchronization

threading.py

import time
from random import random
from threading import Thread, Lock

"""
Python's GIL ensures that non IO ops will execute sequentially

So no need to sync the followings
  s = store + 1
  store = s
"""

l = Lock()
store = 0

def doit():
  with l:
    global store
    s = store + 1
    time.sleep(random()) # IO op
    store = s


threads = []
for i in range(10):
  t = Thread(target=doit)
  t.start()
  threads.append(t)

  
# without synchronization, this takes about 1 sec
# with synchronization, this takes 10 sec
time.sleep(1)  
for t in threads:
  t.join()

print(store) # 10