python threading lock example

synchronize.py

import threading
import time

from functools import wraps

FN_LOCKS = {}

class Lock(object):
    def __init__(self, func_id):
        global FN_LOCKS
        if func_id in FN_LOCKS:
            self.lock = FN_LOCKS[func_id]
        else:
            self.lock = threading.Lock()
            FN_LOCKS[func_id] = self.lock

    def __enter__(self):
        self.lock.acquire()
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.lock.release()


def synchronize(fn):
    @wraps(fn)
    def decorated(*args, **kwargs):
        with Lock(id(fn)):
            ret = fn(*args, **kwargs)
        return ret

    return decorated


counter = 0

@synchronize
def increment_and_print():
    global counter
    time.sleep(counter)
    counter += 1
    print counter


threads = []

for i in range(10):
    print "Starting thread {}".format(i)
    t = threading.Thread(target=increment_and_print)
    t.start()
    threads.append(t)

for t in threads:
    t.join()