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, 直到內部的標志位為True時. 如果在內部的標志位在進入時為True時, 立即返回. 否則, 阻塞直到其他線程調用set()方法將標準位設為True, 或者到達了可選的timeout時間.


  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.

  當給定了timeout參數且不為None, 它應該是一個浮點數，以秒為單位指定操作的超時（或是分數）。

  此方法在退出時返回內部標志，因此除非給定了超時且操作超時，否則它將始終返回True。


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

  2.7版本以前, 這個方法總會返回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()   # 用于暫停線程的標識
    self.__flag.set()    # 設置為True
    self.__running = threading.Event()   # 用于停止線程的標識
    self.__running.set()   # 將running設置為True

  def run(self):
    while self.__running.isSet():
      self.__flag.wait()   # 為True時立即返回, 為False時阻塞直到內部的標識位為True后返回
      print time.time()
      time.sleep(1)

  def pause(self):
    self.__flag.clear()   # 設置為False, 讓線程阻塞

  def resume(self):
    self.__flag.set()  # 設置為True, 讓線程停止阻塞

  def stop(self):
    self.__flag.set()    # 將線程從暫停狀態(tài)恢復, 如何已經暫停的話
    self.__running.clear()    # 設置為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()