python 两线程同时运行

单线程多定时任务

前言：公司业务需求，实例当中大量需要启动定时器的操作；大家都知道python中的定时器用的是threading.Timer，每当启动一个定时器时，程序内部起了一个线程，定时器触发执行结束后，线程自动销毁；这里就涉及到一个问题，如果同时有大量启动定时器的需求时，内部线程过多，程序肯定就崩了，有没有启一个线程就能完成定时器的操作呢？网上查了一些资料，还没有看到能解决目前问题的现成代码，不如自己搞一个试试

1、初始版本：

思路：定时器，说白了就是延时执行指定的程序，目前自己重构python里面的定时器不太现实，能力达不到，所以延时操作时还得用到系统定时器，不过我们可以改一下规则；把所有要进行定时操作的程序添加到特定列表中，把列表中定时时间最短程序拿出来，进行threading.Timer(time，callback)绑定，等时间超时触发自定义的callback，执行刚刚列表取出的程序；然后把时间更新，再次把列表中时间最短的程序拿出了，继续threading.Timer绑定，不断的迭代循环；当有新的定时任务加入到列表时，把当前的threading.Timer绑定取消，更新列表中的时间，再次取出最短时间，进行threading.Timer绑定......

代码：

import threading
import time
class Timer():
'''单线程下的定时器'''
def __init__(self):
self.queues = []
self.timer = None
self.last_time = time.time()
def start(self):
item = self.get()
if item:
self.timer = threading.Timer(item[0],self.execute)
self.timer.start()
def add(self,item):
print('add',item)
self.flush_time()
self.queues.append(item)
self.queues.sort(key=lambda x:x[0])
if self.timer:
self.timer.cancel()
self.timer = None
self.start()
def get(self):
item = None
if len(self.queues) > 0:
item = self.queues[0]
return item
def pop(self):
item = None
if len(self.queues) > 0:
item = self.queues.pop(0)
return item
def flush_time(self):
curr_time = time.time()
for i in self.queues:
i[0] = i[0] - (curr_time - self.last_time)
self.last_time = curr_time
def execute(self):
# if self.timer:
# self.timer.cancel()
# self.timer = None
item = self.pop()
self.flush_time()
if item:
callback = item[1]
args = item[0]
callback(args)
self.start()
执行及输出：


if __name__ == '__main__':#检测线程数
deffunc():whileTrue:print(threading.active_count())
time.sleep(1)
f1= threading.Thread(target=func)
f1.start()importlogging
logging.basicConfig(level=logging.INFO,format="%(asctime)s %(message)s", datefmt="%m/%d/%Y %H:%M:%S [%A]")def func1(*args):
logging.info('func1 %s'%args)#time.sleep(5)
def func2(*args):
logging.info('func2 %s' %args)#time.sleep(5)
def func3(*args):
logging.info('func3 %s' %args)#time.sleep(5)
def func4(*args):
logging.info('func4 %s' %args)#time.sleep(5)
def func5(*args):
logging.info('func5 %s' %args)#time.sleep(5)
#测试
t1 =Timer()
logging.info('start')
t1.add([5,func1])
time.sleep(0.5)
t1.add([4,func2])
time.sleep(0.5)
t1.add([3,func3])
time.sleep(0.5)
t1.add([2,func4])
time.sleep(0.5)
t1.add([1,func5])
time.sleep(5)
t1.add([1,func1])
t1.add([2,func2])
t1.add([3,func3])
t1.add([4,func4])
t1.add([5,func5])#输出
#2
#07/27/2017 10:36:47 [Thursday] start
#add [5, ]
#add [4, ]
#3
#add [3, ]
#add [2, ]
#3
#add [1, ]
#3
#07/27/2017 10:36:50 [Thursday] func5 1
#07/27/2017 10:36:51 [Thursday] func4 0.498349666595459
#3
#07/27/2017 10:36:51 [Thursday] func3 0.49782633781433105
#07/27/2017 10:36:52 [Thursday] func2 0.49848270416259766
#3
#07/27/2017 10:36:52 [Thursday] func1 0.48449039459228516
#2
#2
#add [1, ]
#add [2, ]
#add [3, ]
#add [4, ]
#add [5, ]
#3
#07/27/2017 10:36:55 [Thursday] func1 0.9990766048431396
#3
#07/27/2017 10:36:56 [Thursday] func2 0.9988017082214355
#3
#07/27/2017 10:36:57 [Thursday] func3 0.99928879737854
#07/27/2017 10:36:58 [Thursday] func4 0.9991350173950195
#3
#3
#07/27/2017 10:36:59 [Thursday] func5 0.9988160133361816
执行代码
注：查看代码输出，所有的定时器都按照标定的时间依次执行，非常完美，一切看起来很美好，只是看起来，呵呵哒，当你把func里面的time.sleep(5)启用后，线程数蹭蹭的上来了;原因是上个定时器callback还是执行中，下个定时器已经启动了，这时就又新增了一个线程，哎,失败
2、修订版本
思路：利用生成者消费者模型,用到threading.Condition条件变量；强制永远启用的是一个Timer!
代码：
import time
import threading
import logging
class NewTimer(threading.Thread):
'''单线程下的定时器'''
def __init__(self):
super().__init__()
self.queues = []
self.timer = None
self.cond = threading.Condition()
def run(self):
while True:
# print('NewTimer',self.queues)
self.cond.acquire()
item = self.get()
callback = None
if not item:
logging.info('NewTimer wait')
self.cond.wait()
elif item[0] <= time.time():
new_item = self.pop()
callback = new_item[1]
else:
logging.info('NewTimer start sys timer and wait')
self.timer = threading.Timer(item[0]-time.time(),self.execute)
self.timer.start()
self.cond.wait()
self.cond.release()
if callback:
callback(item[0])
def add(self, item):
# print('add', item)
self.cond.acquire()
item[0] = item[0] + time.time()
self.queues.append(item)
self.queues.sort(key=lambda x: x[0])
logging.info('NewTimer add notify')
if self.timer:
self.timer.cancel()
self.timer = None
self.cond.notify()
self.cond.release()
def pop(self):
item = None
if len(self.queues) > 0:
item = self.queues.pop(0)
return item
def get(self):
item = None
if len(self.queues) > 0:
item = self.queues[0]
return item
def execute(self):
logging.info('NewTimer execute notify')
self.cond.acquire()
self.cond.notify()
self.cond.release()
执行及输出：


if __name__ == '__main__':deffunc():whileTrue:print(threading.active_count())
time.sleep(1)
f1= threading.Thread(target=func)
f1.start()
logging.basicConfig(level=logging.INFO,format="%(asctime)s %(message)s", datefmt="%m/%d/%Y %H:%M:%S [%A]")
newtimer=NewTimer()
newtimer.start()def func1(*args):
logging.info('func1 %s'%args)
time.sleep(5)def func2(*args):
logging.info('func2 %s' %args)
time.sleep(5)def func3(*args):
logging.info('func3 %s' %args)
time.sleep(5)def func4(*args):
logging.info('func4 %s' %args)
time.sleep(5)def func5(*args):
logging.info('func5 %s' %args)
time.sleep(5)
newtimer.add([5,func1])
newtimer.add([4,func2])
newtimer.add([3,func3])
newtimer.add([2,func4])
newtimer.add([1,func5])
time.sleep(1)
newtimer.add([1,func1])
newtimer.add([2,func2])
newtimer.add([3,func3])
newtimer.add([4,func4])
newtimer.add([5,func5])#输出#2#07/27/2017 11:26:19 [Thursday] NewTimer wait#07/27/2017 11:26:19 [Thursday] NewTimer add notify#07/27/2017 11:26:19 [Thursday] NewTimer add notify#07/27/2017 11:26:19 [Thursday] NewTimer add notify#07/27/2017 11:26:19 [Thursday] NewTimer add notify#07/27/2017 11:26:19 [Thursday] NewTimer add notify#07/27/2017 11:26:19 [Thursday] NewTimer start sys timer and wait#07/27/2017 11:26:20 [Thursday] NewTimer execute notify#4#07/27/2017 11:26:20 [Thursday] func5 1501125980.2175007#07/27/2017 11:26:20 [Thursday] NewTimer add notify#07/27/2017 11:26:20 [Thursday] NewTimer add notify#07/27/2017 11:26:20 [Thursday] NewTimer add notify#07/27/2017 11:26:20 [Thursday] NewTimer add notify#07/27/2017 11:26:20 [Thursday] NewTimer add notify#3#3#3#3#3#07/27/2017 11:26:25 [Thursday] func4 1501125981.2175007#3#3#3#3#07/27/2017 11:26:30 [Thursday] func1 1501125981.218279#3#3#3#3#3#3#07/27/2017 11:26:35 [Thursday] func3 1501125982.2175007#3#3#3#3#07/27/2017 11:26:40 [Thursday] func2 1501125982.218279#3#3#3#3#3#07/27/2017 11:26:45 [Thursday] func2 1501125983.2175007#3#3#3#3#3#07/27/2017 11:26:50 [Thursday] func3 1501125983.218279#3#3#3#3#3#07/27/2017 11:26:55 [Thursday] func1 1501125984.2175007#3#3#3#3#3#07/27/2017 11:27:00 [Thursday] func4 1501125984.218279#3#3#3#3#3#07/27/2017 11:27:05 [Thursday] func5 1501125985.218279#3#3#3#3#3#07/27/2017 11:27:10 [Thursday] NewTimer wait

输出

注：这次无论如何测试线程数也不会蹭蹭的上涨，同时可以实现多定时器任务要求；缺点：用到了两线程，没有用到单线程去实现，第二时间精准度问题，需要等待上个定时程序执行完毕，程序才能继续运行