python 线程的暂停, 恢复, 退出详解及实例

wait([timeout])

  Block until the internal flag is true. If the internal flag is true on entry, return immediately. Otherwise, block until another thread calls set() to set the flag to true, or until the optional timeout occurs.

  阻塞, 直到内部的标志位为True时. 如果在内部的标志位在进入时为True时, 立即返回. 否则, 阻塞直到其他线程调用set()方法将标准位设为True, 或者到达了可选的timeout时间.


  When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions thereof).

  This method returns the internal flag on exit, so it will always return True except if a timeout is given and the operation times out.

  当给定了timeout参数且不为None, 它应该是一个浮点数，以秒为单位指定操作的超时（或是分数）。

  此方法在退出时返回内部标志，因此除非给定了超时且操作超时，否则它将始终返回True。


  Changed in version 2.7: Previously, the method always returned None.

  2.7版本以前, 这个方法总会返回None.

#!/usr/bin/env python
# coding: utf-8

import threading
import time


class Job(threading.Thread):

  def __init__(self, *args, **kwargs):
    super(Job, self).__init__(*args, **kwargs)
    self.__flag = threading.Event()   # 用于暂停线程的标识
    self.__flag.set()    # 设置为True
    self.__running = threading.Event()   # 用于停止线程的标识
    self.__running.set()   # 将running设置为True

  def run(self):
    while self.__running.isSet():
      self.__flag.wait()   # 为True时立即返回, 为False时阻塞直到内部的标识位为True后返回
      print time.time()
      time.sleep(1)

  def pause(self):
    self.__flag.clear()   # 设置为False, 让线程阻塞

  def resume(self):
    self.__flag.set()  # 设置为True, 让线程停止阻塞

  def stop(self):
    self.__flag.set()    # 将线程从暂停状态恢复, 如何已经暂停的话
    self.__running.clear()    # 设置为False  

a = Job()
a.start()
time.sleep(3)
a.pause()
time.sleep(3)
a.resume()
time.sleep(3)
a.pause()
time.sleep(2)
a.stop()