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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