线程池

一、在python3中开多线程

使用concurrent.futures模块，这个模块是python3中自带的模块

• 1、开个线程池的代码

  import time
  from concurrent.futures import ThreadPoolExecutor
  
  def get_html(times):
      time.sleep(times)
      print('获取页面数据:{}'.format(times))
      return times
  
  if __name__ == "__main__":
      # 最大可以容许2个线程进程
      executor = ThreadPoolExecutor(max_workers=2)
      task1 = executor.submit(get_html, 3)
      task2 = executor.submit(get_html, 2)
  

• 2、一些方法介绍

  • 1.submit()向线程池中提交一个方法
  • 2.done()查看结果
  • 3.cancel()取消(只有在没启动的时候才能取消)
  • 4.result()获取线程池中执行的结果

• 3、使用as_completed批量提交任务(无顺序的执行)

  from concurrent.futures import ThreadPoolExecutor, as_completed, wait
  import time
  
  def get_html(times):
      time.sleep(times)
      print('获取页面数据:{}'.format(times))
      return times
  
  if __name__ == "__main__":
      urls_list = [4, 2, 1, 3, 6]
      executor = ThreadPoolExecutor(max_workers=2)
      all_task = [executor.submit(get_html, (url)) for url in urls_list]
      for item in as_completed(all_task):
          data = item.result()
          print('main==>', data)
  

• 4、使用map批量提交任务(有顺序的执行)

  from concurrent.futures import ThreadPoolExecutor, as_completed, wait
  import time
  
  def get_html(times):
      time.sleep(times)
      print('获取页面数据:{}'.format(times))
      return times
  
  if __name__ == "__main__":
      urls_list = [4, 2, 1, 3, 6]
      executor = ThreadPoolExecutor(max_workers=2)
  
      for item in executor.map(get_html, urls_list):
          print('main==>', item)
  
      print('结束程序')
  

• 5、wait()等待什么执行完后进行下面的