from dateutil import tz

import threading
try:
    from threading import Barrier
except ImportError:
    from threading import Semaphore

    class Barrier(object):
        def __init__(self, n):
            self.n = n
            self.count = 0
            self.mutex = Semaphore(1)
            self.barrier = Semaphore(0)

        def wait(self):
            self.mutex.acquire()
            self.count = self.count + 1
            self.mutex.release()
            if self.count == self.n:
                self.barrier.release()
            self.barrier.acquire()
            self.barrier.release()

N = 2500
b = Barrier(N)
b2 = Barrier(N-1)

def constructor():
    b.wait()
    tz.tzstr("EST5EDT")
    b2.wait()

for i in range(N):
    threading.Thread(target=constructor).start()

b2.wait()
print("Done")