ReusableBarrier 模式可以保证一组线程可以全部执行到某一语句后才继续往下执行。

# -*- coding: utf-8 -*-
import threading
import time
from threading import Semaphore, Thread


class ReusableBarrierClass:
    def __init__(self, thread_count):
        self.thread_count = thread_count
        self.count = 0
        self.mutex = Semaphore(1)
        self.turnstile = Semaphore(0)
        self.turnstile2 = Semaphore(1)

    def __enter__(self):
        self.mutex.acquire()
        self.count += 1
        if self.count == self.thread_count:
            print(u"当前线程号", threading.currentThread().getName(), u" turnstile 打开")
            self.turnstile.release()
            self.turnstile2.acquire()
        self.mutex.release()

        self.turnstile.acquire()
        self.turnstile.release()

    def __exit__(self, exc_type, exc_value, traceback):
        self.mutex.acquire()
        self.count -= 1
        if self.count == 0:
            print(u"当前线程号", threading.currentThread().getName(), u" turnstile 重新关闭")
            self.turnstile.acquire()
            self.turnstile2.release()
        self.mutex.release()

        self.turnstile2.acquire()
        self.turnstile2.release()


barrier = ReusableBarrierClass(3)


def worker(br, idx):
    print(u"当前线程号", threading.currentThread().getName(), u" 函数进入")
    with br:
        print(u"当前线程号", threading.currentThread().getName(), u" 正在执行")
        time.sleep(idx * 2)
        print(u"当前线程号", threading.currentThread().getName(), u" 执行完毕")
    print(u"当前线程号", threading.currentThread().getName(), u" 函数退出执行")


for i in range(barrier.thread_count):
    Thread(target=worker, args=(barrier, i)).start()