单线程多定时任务 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 def func(): while true: print(threading.active_count()) time.sleep(1) f1 = threading.thread(target=func) f1.start() import logging 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, <function func1 at 0x000000d79fc77e18>] # add [4, <function func2 at 0x000000d79fca8488>] # 3 # add [3, <function func3 at 0x000000d79fca8510>] # add [2, <function func4 at 0x000000d79fca8598>] # 3 # add [1, <function func5 at 0x000000d79fca8620>] # 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, <function func1 at 0x000000d79fc77e18>] # add [2, <function func2 at 0x000000d79fca8488>] # add [3, <function func3 at 0x000000d79fca8510>] # add [4, <function func4 at 0x000000d79fca8598>] # add [5, <function func5 at 0x000000d79fca8620>] # 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__': def func(): while true: 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
以上就是python开发之多个定时任务在单线程下执行的实例分析的详细内容。