Python threading 單線程 timer重複調用函數

標籤：nis   not   調用函數   read   資源   \n   waiting   python   個人   

項目中需要使用定時器，每次都使用構造器函數調用：

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

列印線程後發現，每次都會建立一個新的子線程，雖然活躍的線程只有一個，但是也是種資源浪費：

print("threading active = {} \n   \n".format(threading.enumerate()))#列印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)>]

閱讀源碼和文檔

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

發現，其實Timer是threading的子類，用wait實現了定時效果，綁定了入參function，於是修改代碼如下

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

列印結果：

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)>]

始終只有一個線程且重複調用函數方法~End~

? ?
? ?
? ?

友情連結:個人網站???????技術部落格 ???????簡書首頁

Python threading 單線程 timer重複調用函數