我想每 0.5 秒触发一次功能，并且能够启动和停止并重置计时器。我不太了解 Python 线程是如何工作的，并且在使用 Python 计时器时遇到了困难。
RuntimeError: threads can only be started once但是，当我执行threading.timer.start()两次时，我不断得到。有解决办法吗？我尝试threading.timer.cancel()在每次开始之前申请。
伪代码：
t=threading.timer(0.5,function)
while True:
t.cancel()
t.start()
最好的方法是启动一次定时器线程。在您的计时器线程中，您将编写以下代码
class MyThread(Thread):
def __init__(self, event):
Thread.__init__(self)
self.stopped = event
def run(self):
while not self.stopped.wait(0.5):
print("my thread")
# call a function
在启动计时器的代码中，您可以随后set通过停止事件来停止计时器。
stopFlag = Event()
thread = MyThread(stopFlag)
thread.start()
# this will stop the timer
stopFlag.set()
import threading
def setInterval(interval):
def decorator(function):
def wrapper(*args, **kwargs):
stopped = threading.Event()
def loop(): # executed in another thread
while not stopped.wait(interval): # until stopped
function(*args, **kwargs)
t = threading.Thread(target=loop)
t.daemon = True # stop if the program exits
t.start()
return stopped
return wrapper
return decorator
用法：
@setInterval(.5)
def function():
"..."
stop = function() # start timer, the first call is in .5 seconds
stop.set() # stop the loop
stop = function() # start new timer
# ...
stop.set()
或者这里有相同的功能，但作为独立功能而不是装饰器：
cancel_future_calls = call_repeatedly(60, print, "Hello, World")
# ...
cancel_future_calls()
对Hans Then 的回答稍作改进，我们可以将 Timer 函数子类化。以下成为我们完整的“重复计时器”代码，它可以用作 threading.Timer 的替代品，具有所有相同的参数：
from threading import Timer
class RepeatTimer(Timer):
def run(self):
while not self.finished.wait(self.interval):
self.function(*self.args, **self.kwargs)
使用示例：
def dummyfn(msg="foo"):
print(msg)
timer = RepeatTimer(1, dummyfn)
timer.start()
time.sleep(5)
timer.cancel()
产生以下输出：
foo
foo
foo
foo
和
timer = RepeatTimer(1, dummyfn, args=("bar",))
timer.start()
time.sleep(5)
timer.cancel()
生产
bar
bar
bar
bar
使用计时器线程-
from threading import Timer,Thread,Event
class perpetualTimer():
def __init__(self,t,hFunction):
self.t=t
self.hFunction = hFunction
self.thread = Timer(self.t,self.handle_function)
def handle_function(self):
self.hFunction()
self.thread = Timer(self.t,self.handle_function)
self.thread.start()
def start(self):
self.thread.start()
def cancel(self):
self.thread.cancel()
def printer():
print 'ipsem lorem'
t = perpetualTimer(5,printer)
t.start()
这可以通过t.cancel()
为了按照 OP 的要求使用 Timer 提供正确的答案，我将改进swapnil jariwala 的答案：
from threading import Timer
class InfiniteTimer():
"""A Timer class that does not stop, unless you want it to."""
def __init__(self, seconds, target):
self._should_continue = False
self.is_running = False
self.seconds = seconds
self.target = target
self.thread = None
def _handle_target(self):
self.is_running = True
self.target()
self.is_running = False
self._start_timer()
def _start_timer(self):
if self._should_continue: # Code could have been running when cancel was called.
self.thread = Timer(self.seconds, self._handle_target)
self.thread.start()
def start(self):
if not self._should_continue and not self.is_running:
self._should_continue = True
self._start_timer()
else:
print("Timer already started or running, please wait if you're restarting.")
def cancel(self):
if self.thread is not None:
self._should_continue = False # Just in case thread is running and cancel fails.
self.thread.cancel()
else:
print("Timer never started or failed to initialize.")
def tick():
print('ipsem lorem')
# Example Usage
t = InfiniteTimer(0.5, tick)
t.start()
我已经更改了 swapnil-jariwala 代码中的一些代码来制作一个小控制台时钟。
from threading import Timer, Thread, Event
from datetime import datetime
class PT():
def __init__(self, t, hFunction):
self.t = t
self.hFunction = hFunction
self.thread = Timer(self.t, self.handle_function)
def handle_function(self):
self.hFunction()
self.thread = Timer(self.t, self.handle_function)
self.thread.start()
def start(self):
self.thread.start()
def printer():
tempo = datetime.today()
h,m,s = tempo.hour, tempo.minute, tempo.second
print(f"{h}:{m}:{s}")
t = PT(1, printer)
t.start()
输出
>>> 11:39:11
11:39:12
11:39:13
11:39:14
11:39:15
11:39:16
...
此代码使用 tkinter 将时钟计时器放在一个小窗口中
from threading import Timer, Thread, Event
from datetime import datetime
import tkinter as tk
app = tk.Tk()
lab = tk.Label(app, text="Timer will start in a sec")
lab.pack()
class perpetualTimer():
def __init__(self, t, hFunction):
self.t = t
self.hFunction = hFunction
self.thread = Timer(self.t, self.handle_function)
def handle_function(self):
self.hFunction()
self.thread = Timer(self.t, self.handle_function)
self.thread.start()
def start(self):
self.thread.start()
def cancel(self):
self.thread.cancel()
def printer():
tempo = datetime.today()
clock = "{}:{}:{}".format(tempo.hour, tempo.minute, tempo.second)
try:
lab['text'] = clock
except RuntimeError:
exit()
t = perpetualTimer(1, printer)
t.start()
app.mainloop()
from threading import Timer, Thread, Event
from datetime import datetime
class perpetualTimer():
def __init__(self, t, hFunction):
self.t = t
self.hFunction = hFunction
self.thread = Timer(self.t, self.handle_function)
def handle_function(self):
self.hFunction()
self.thread = Timer(self.t, self.handle_function)
self.thread.start()
def start(self):
self.thread.start()
def cancel(self):
self.thread.cancel()
x = datetime.today()
start = x.second
def printer():
global questions, counter, start
x = datetime.today()
tempo = x.second
if tempo - 3 > start:
show_ans()
#print("\n{}:{}:{}".format(tempo.hour, tempo.minute, tempo.second), end="")
print()
print("-" + questions[counter])
counter += 1
if counter == len(answers):
counter = 0
def show_ans():
global answers, c2
print("It is {}".format(answers[c2]))
c2 += 1
if c2 == len(answers):
c2 = 0
questions = ["What is the capital of Italy?",
"What is the capital of France?",
"What is the capital of England?",
"What is the capital of Spain?"]
answers = "Rome", "Paris", "London", "Madrid"
counter = 0
c2 = 0
print("Get ready to answer")
t = perpetualTimer(3, printer)
t.start()
输出：
Get ready to answer
>>>
-What is the capital of Italy?
It is Rome
-What is the capital of France?
It is Paris
-What is the capital of England?
...
我必须为一个项目做这个。我最终做的是为该函数启动一个单独的线程
t = threading.Thread(target =heartbeat, args=(worker,))
t.start()
****心跳是我的功能，工人是我的论据之一****
在我的心跳功能内部：
def heartbeat(worker):
while True:
time.sleep(5)
#all of my code
因此，当我启动线程时，该函数将反复等待 5 秒，运行我的所有代码，并无限期地执行此操作。如果要终止进程，只需终止线程。
我喜欢 right2clicky 的回答，尤其是它不需要在每次计时器滴答时都拆除线程并创建一个新线程。此外，创建一个带有定期调用的计时器回调的类是一个简单的覆盖。这是我的正常用例：
class MyClass(RepeatTimer):
def __init__(self, period):
super().__init__(period, self.on_timer)
def on_timer(self):
print("Tick")
if __name__ == "__main__":
mc = MyClass(1)
mc.start()
time.sleep(5)
mc.cancel()
我已经实现了一个用作计时器的类。
如果有人需要，我将链接留在这里： https ://github.com/ivanhalencp/python/tree/master/xTimer
这是使用函数而不是类的替代实现。受上述@Andrew Wilkins 的启发。
因为等待比睡眠更准确（它考虑了函数运行时）：
import threading
PING_ON = threading.Event()
def ping():
while not PING_ON.wait(1):
print("my thread %s" % str(threading.current_thread().ident))
t = threading.Thread(target=ping)
t.start()
sleep(5)
PING_ON.set()
除了使用线程的上述出色答案之外，如果您必须使用主线程或更喜欢异步方法 - 我在aio_timers Timer 类周围包装了一个短类（以启用重复）
import asyncio
from aio_timers import Timer
class RepeatingAsyncTimer():
def __init__(self, interval, cb, *args, **kwargs):
self.interval = interval
self.cb = cb
self.args = args
self.kwargs = kwargs
self.aio_timer = None
self.start_timer()
def start_timer(self):
self.aio_timer = Timer(delay=self.interval,
callback=self.cb_wrapper,
callback_args=self.args,
callback_kwargs=self.kwargs
)
def cb_wrapper(self, *args, **kwargs):
self.cb(*args, **kwargs)
self.start_timer()
from time import time
def cb(timer_name):
print(timer_name, time())
print(f'clock starts at: {time()}')
timer_1 = RepeatingAsyncTimer(interval=5, cb=cb, timer_name='timer_1')
timer_2 = RepeatingAsyncTimer(interval=10, cb=cb, timer_name='timer_2')
时钟开始于：16024388 40 .9690785
计时器_ 1 16024388 45 .980087
计时器_2 16024388 50 .9806316
计时器_ 1 16024388 50 .9808934
计时器_ 1 16024388 55 .9863033
timer_2 16024388 60 .9868324 _
计时器_ 1 16024388 60 .9876585
from threading import Timer
def TaskManager():
#do stuff
t = Timer( 1, TaskManager )
t.start()
TaskManager()
这是一个小样本，它将有助于更好地理解它是如何运行的。最后的函数 taskManager() 创建对其自身的延迟函数调用。
尝试更改“dalay”变量，您将能够看到差异
from threading import Timer, _sleep
# ------------------------------------------
DATA = []
dalay = 0.25 # sec
counter = 0
allow_run = True
FIFO = True
def taskManager():
global counter, DATA, delay, allow_run
counter += 1
if len(DATA) > 0:
if FIFO:
print("["+str(counter)+"] new data: ["+str(DATA.pop(0))+"]")
else:
print("["+str(counter)+"] new data: ["+str(DATA.pop())+"]")
else:
print("["+str(counter)+"] no data")
if allow_run:
#delayed method/function call to it self
t = Timer( dalay, taskManager )
t.start()
else:
print(" END task-manager: disabled")
# ------------------------------------------
def main():
DATA.append("data from main(): 0")
_sleep(2)
DATA.append("data from main(): 1")
_sleep(2)
# ------------------------------------------
print(" START task-manager:")
taskManager()
_sleep(2)
DATA.append("first data")
_sleep(2)
DATA.append("second data")
print(" START main():")
main()
print(" END main():")
_sleep(2)
DATA.append("last data")
allow_run = False
我想出了另一个 SingleTon 类的解决方案。请告诉我是否有任何内存泄漏。
import time,threading
class Singleton:
__instance = None
sleepTime = 1
executeThread = False
def __init__(self):
if Singleton.__instance != None:
raise Exception("This class is a singleton!")
else:
Singleton.__instance = self
@staticmethod
def getInstance():
if Singleton.__instance == None:
Singleton()
return Singleton.__instance
def startThread(self):
self.executeThread = True
self.threadNew = threading.Thread(target=self.foo_target)
self.threadNew.start()
print('doing other things...')
def stopThread(self):
print("Killing Thread ")
self.executeThread = False
self.threadNew.join()
print(self.threadNew)
def foo(self):
print("Hello in " + str(self.sleepTime) + " seconds")
def foo_target(self):
while self.executeThread:
self.foo()
print(self.threadNew)
time.sleep(self.sleepTime)
if not self.executeThread:
break
sClass = Singleton()
sClass.startThread()
time.sleep(5)
sClass.getInstance().stopThread()
sClass.getInstance().sleepTime = 2
sClass.startThread()
这是连续运行定时器的示例代码。只需在耗尽时创建一个新计时器并调用相同的函数。不是最好的方法，但也可以这样做。
import threading
import time
class ContinousTimer():
def __init__(self):
self.timer = None
def run(self, msg='abc'):
print(msg)
self.timer = threading.Timer(interval=2, function=self.run, args=(msg, ))
self.timer.start()
if __name__ == "__main__":
t = ContinousTimer()
try:
t.run(msg="Hello")
while True:
time.sleep(0.1)
except KeyboardInterrupt:
# Cancel Timer
t.timer.cancel()