Python Threading Single-threaded timer repeating call function

A timer is required in the project, and each time a constructor function call is used:

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

After the print thread is discovered, a new child thread is created each time, although there is only one active thread, but it is also a waste of resources:

  print ("Threading active = {} \ n \ nthe". 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);]  

Read the source code and documentation

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

found that, in fact, the timer is a subclass of threading, with wait to achieve the timing effect, binding the entry function, so the code is modified as follows

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

Printing results:

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)>]

Always have only one thread and call the function method repeatedly ~end~

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Python Threading Single-threaded timer repeating call function