Python threading 单线程 timer重复调用函数

时间:2023-03-08 16:10:04
Python threading 单线程 timer重复调用函数

项目中需要使用定时器,每次都使用构造器函数调用:

timer = threading.Timer(timerFlag, upload_position)
timer.start()

打印线程后发现,每次都会创建一个新的子线程,虽然活跃的线程只有一个,但是也是种资源浪费:

print("threading active = {} \n   \n".format(threading.enumerate()))

#打印
threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145498161152)>]
threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145498161152)>]
threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145498161152)>] threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-2, started 123145503416320)>]
threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-2, started 123145503416320)>] threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-3, started 123145498161152)>]
threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-3, started 123145498161152)>]

阅读源码和文档

class Timer(Thread):
"""Call a function after a specified number of seconds: t = Timer(30.0, f, args=None, kwargs=None)
t.start()
t.cancel() # stop the timer's action if it's still waiting """ def __init__(self, interval, function, args=None, kwargs=None):
Thread.__init__(self)
self.interval = interval
self.function = function
self.args = args if args is not None else []
self.kwargs = kwargs if kwargs is not None else {}
self.finished = Event() def cancel(self):
"""Stop the timer if it hasn't finished yet."""
self.finished.set() def run(self):
self.finished.wait(self.interval)
if not self.finished.is_set():
self.function(*self.args, **self.kwargs)
self.finished.set() # Special thread class to represent the main thread
# This is garbage collected through an exit handler

发现,其实Timer是threading的子类,用wait实现了定时效果,绑定了入参function,于是修改代码如下


def startTimer():
global timer
if timer != None:
timer.finished.wait(timerFlag)
timer.function()
else:
timer = threading.Timer(timerFlag, upload_position)
timer.start()

打印结果:


threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145516048384)>] threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145516048384)>] threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145516048384)>] threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145516048384)>] threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145516048384)>] threading active = [<_MainThread(MainThread, stopped 140735596835712)>, <Timer(Thread-1, started 123145516048384)>]

始终只有一个线程且重复调用函数方法~End~

   

   

   

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