每n秒運行一段代碼

Question

有沒有辦法，例如每n秒打印一次Hello World!？例如，程序會通過我有的任何代碼，然後一旦它已經5秒鐘（與time.sleep()）它會執行該代碼。我會用它來更新文件，但不打印Hello World。

例如：

startrepeat("print('Hello World')", .01) # Repeats print('Hello World') ever .01 seconds 

for i in range(5): 
    print(i) 

>> Hello World! 
>> 0 
>> 1 
>> 2 
>> Hello World! 
>> 3 
>> Hello World! 
>> 4 

Answer 1

import threading 

def printit(): 
    threading.Timer(5.0, printit).start() 
    print "Hello, World!" 

printit() 

# continue with the rest of your code 

Answer 2

def update(): 
    import time 
    while True: 
     print 'Hello World!' 
     time.sleep(5) 

這將作爲一個功能運行。 while True:使它永遠運行。如果您需要，您可以隨時將其從功能中取出。

Answer 3

你可以開始一個單獨的線程，其唯一的職責是計數5秒，更新文件，重複。你不希望這個單獨的線程干擾你的主線程。

Answer 4

我的卑微就這個題目，亞歷克斯·馬爾泰利的答案的推廣，用的start（）和stop（）控制：

from threading import Timer 

class RepeatedTimer(object): 
    def __init__(self, interval, function, *args, **kwargs): 
     self._timer  = None 
     self.interval = interval 
     self.function = function 
     self.args  = args 
     self.kwargs  = kwargs 
     self.is_running = False 
     self.start() 

    def _run(self): 
     self.is_running = False 
     self.start() 
     self.function(*self.args, **self.kwargs) 

    def start(self): 
     if not self.is_running: 
      self._timer = Timer(self.interval, self._run) 
      self._timer.start() 
      self.is_running = True 

    def stop(self): 
     self._timer.cancel() 
     self.is_running = False 

用法：

from time import sleep 

def hello(name): 
    print "Hello %s!" % name 

print "starting..." 
rt = RepeatedTimer(1, hello, "World") # it auto-starts, no need of rt.start() 
try: 
    sleep(5) # your long-running job goes here... 
finally: 
    rt.stop() # better in a try/finally block to make sure the program ends! 

特點：

• 只有標準庫，沒有外部依賴dencies
• start()和stop()是安全的，多次調用，即使定時器已經開始/停止
• 要調用的函數可以有位置和命名參數
• 您可以隨時更改interval，這將是下一個後生效跑。 args，kwargs甚至function也一樣！

Answer 5

保存自己精神分裂症發作，並使用先進的Python調度： http://pythonhosted.org/APScheduler

的代碼是如此簡單：

from apscheduler.scheduler import Scheduler 

sched = Scheduler() 
sched.start() 

def some_job(): 
    print "Every 10 seconds" 

sched.add_interval_job(some_job, seconds = 10) 

.... 
sched.shutdown() 

Answer 6

這裏是不創建一個新的線程版本每n秒：

from threading import Event, Thread 

def call_repeatedly(interval, func, *args): 
    stopped = Event() 
    def loop(): 
     while not stopped.wait(interval): # the first call is in `interval` secs 
      func(*args) 
    Thread(target=loop).start()  
    return stopped.set 

該事件用於停止th Ë重複：

cancel_future_calls = call_repeatedly(5, print, "Hello, World") 
# do something else here... 
cancel_future_calls() # stop future calls 

見Improve current implementation of a setInterval python

Answer 7

下面是一個簡單的例子與APScheduler 3.00+兼容：

# note that there are many other schedulers available 
from apscheduler.schedulers.background import BackgroundScheduler 

sched = BackgroundScheduler() 

def some_job(): 
    print('Every 10 seconds') 

# seconds can be replaced with minutes, hours, or days 
sched.add_job(some_job, 'interval', seconds=10) 
sched.start() 

... 

sched.shutdown() 

或者，你可以使用下面的。與許多替代方案不同，此計時器將精確地執行所需的代碼（無論代碼執行所花費的時間），每隔012秒鐘執行一次所需的代碼。所以如果你無法承受任何漂移，這是一個很好的選擇。

import time 
from threading import Event, Thread 

class RepeatedTimer: 

    """Repeat `function` every `interval` seconds.""" 

    def __init__(self, interval, function, *args, **kwargs): 
     self.interval = interval 
     self.function = function 
     self.args = args 
     self.kwargs = kwargs 
     self.start = time.time() 
     self.event = Event() 
     self.thread = Thread(target=self._target) 
     self.thread.start() 

    def _target(self): 
     while not self.event.wait(self._time): 
      self.function(*self.args, **self.kwargs) 

    @property 
    def _time(self): 
     return self.interval - ((time.time() - self.start) % self.interval) 

    def stop(self): 
     self.event.set() 
     self.thread.join() 


# start timer 
timer = RepeatedTimer(10, print, 'Hello world') 

# stop timer 
timer.stop()