Question

我试图在Python中掌握多线程。我写了这段代码：

import requests
import threading
from time import time,sleep

start_time = time()

class myThread(threading.Thread):
    def __init__(self,threadID,name):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name


     def run(self):
        print(self.name + " Starting")
        start = time()

        url = 'https://stackoverflow.com'
        for i in range(20):
            res = requests.post(url,timeout=5)
        end = time()
        print("Final Thread Time: " + str(end-start) + 'For Thread {}'.format(self.threadID))





  threads = []
  threadID = 1

  for i in range(1,5):
        thread = myThread(threadID,'thread{}'.format(threadID))
        thread.start()
        threads.append(thread)
        threadID += 1
  for t in threads:
      t.join()
  final_time_end = time()
  print("Final Time: " + str(start_time - final_time_end))

所以基本上它在每个帖子中向一个url发送了20个帖子请求。结果是：

Final Thread Time: 6.0695300102 For Thread 3
Final Thread Time: 6.8553800583 For Thread 1
Final Thread Time: 6.9735219479 For Thread 5
Final Thread Time: 6.5822350979 For Thread 4
Final Thread Time: 11.330765152 For Thread 2

我有一个双核CPU，我不明白为什么几乎每次我运行这个脚本时，4个线程几乎在同一时间（6s）完成，但是1个线程大约需要11s（顺便说一句，有时它们都是同时完成。）

当我使用4或3个线程运行此代码时会发生这种情况。最后一个通常需要更多时间才能完成。在最后一个需要更多时间的线程中发生了什么？

python多线程计时

0 个答案: