I found a solution for executing a function periodically every N seconds.
import threading;
def do_every (interval, worker_func, iterations = 0):
if iterations != 1:
threading.Timer (
interval,
do_every, [interval, worker_func, 0 if iterations == 0 else iterations-1]
).start ();
worker_func ();
def print_hw ():
print "hello world";
def print_so ():
print "stackoverflow"
# call print_so every second, 5 times total
do_every (1, print_so, 5);
# call print_hw two times per second, forever
do_every (0.5, print_hw);
When we execute this code it start print "hello world" and "stackoverflow" at the moment execution (at time=0 seconds). What is the possible way to make it printat time=1 second and time=0.5 seconds (not starting at time=0 seconds) without using time.sleep
I would be really hesitant to spawn a new Timer every single time. Timer extends Thread, and no one wants to start a new thread every few seconds.
If we look at the source code for Python, we can provide our own implementation for the Timer class. I don't know Python, so there may be a way to extend the class instead of basically copying all of its code.
The Timer class uses an Event (also in the threading module), to wait the specified amount of time.
import threading;
from threading import Thread;
from threading import Event;
#Extended from a class written by Itamar Shtull-Trauring
class MultiTimer(Thread):
def __init__(self, interval, function, count = 0, 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()
self.count = count
self.infinite = count == 0
def cancel(self):
"""Stop the timer if it hasn't finished yet."""
self.finished.set()
def run(self):
while not self.finished.is_set():
self.finished.wait(self.interval)
if not self.finished.is_set():
self.function(*self.args, **self.kwargs)
self.decrementCount()
def decrementCount(self):
if not self.infinite:
self.count -= 1
if self.count == 0:
self.finished.set()
def hello():
print "hello, world"
#prints "hello, world" 3 times, at time = 2, 4, 6
t = MultiTimer(2.0, hello, 3)
t.start();
#never stops printing "hello, world" every 2 seconds
u = MultiTimer(2.0, hello)
u.start();
I need a sleep() method which can be aborted (as described here or here).
My approach is to let a threading.Event.wait() timeout at the specified duration:
def abortable_sleep(secs, abort_event):
abort_event.wait(timeout=secs)
abort_event.clear()
After calling abortable_sleep(10, _abort) I can now (from another thread) call _event.set(_abort) to let abortable_sleep() terminate before the 10 seconds.
Example:
def sleeping_thread():
_start = time.perf_counter()
print("%f thread started" % (time.perf_counter() - _start))
abortable_sleep(5, _abort)
print("%f thread stopped" % (time.perf_counter() - _start))
if __name__ == '__main__':
_abort = threading.Event()
while True:
threading.Thread(target=sleeping_thread).start()
time.sleep(3)
_abort.set()
time.sleep(1)
Output:
0.000001 thread started
3.002668 thread stopped
0.000002 thread started
3.003014 thread stopped
0.000001 thread started
3.002928 thread stopped
0.000001 thread started
This code is working as expected but I still have some questions:
isn't there an easier way to have s.th. likea sleep() which can be aborted?
can this be done more elegant? E.g. this way I have to be careful with the Event instance which is not bound to an instance of abortable_sleep()
do I have to expect performance issues with high frequency loops like while True: abortable_sleep(0.0001)? How is the wait()-timeout implemented?
I have a wrapper class which basically slaps some sleep semantics on top of an Event. The nice thing is that you only have to pass around a Sleep object, which you can call sleep() on several times if you like (sleep() is not thread safe though) and that you can wake() from another thread.
from threading import Event
class Sleep(object):
def __init__(self, seconds, immediate=True):
self.seconds = seconds
self.event = Event()
if immediate:
self.sleep()
def sleep(self, seconds=None):
if seconds is None:
seconds = self.seconds
self.event.clear()
self.event.wait(timeout=seconds)
def wake(self):
self.event.set()
Usage example:
if __name__ == '__main__':
from threading import Thread
import time
import logging
logger = logging.getLogger()
logger.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(created)d - %(message)s')
handler = logging.StreamHandler()
handler.setFormatter(formatter)
logger.addHandler(handler)
logger.info("sleep")
s = Sleep(3)
logger.info("awake")
def wake_it(sleeper):
time.sleep(1)
logger.info("wakeup!")
sleeper.wake()
logger.info("sleeping again")
s = Sleep(60, immediate=False)
Thread(target=wake_it, args=[s]).start()
s.sleep()
logger.info("awake again")
The above might output something like this:
1423750549 - sleep
1423750552 - awake
1423750552 - sleeping again
1423750553 - wakeup!
1423750553 - awake again
Exactly what you did, but encapsulated in a class.
Due to race conditions, your solution is not always perfectly correct. You should use a threading.BoundedSemaphore() instead. Call aquire() immediately after creating it. When you want to sleep, call acquire() with a timeout, then call release() if the acquire() returned true. To abort the sleep early, call release() from a different thread; this will raise ValueError if there is no sleep in progress.
Using an event instead is problematic if the other thread calls set() at the wrong time (i.e. at any time other than when you are actually waiting on the event).
I'd wrap the sleep/abort function up in a new class:
class AbortableSleep():
def __init__(self):
self._condition = threading.Condition()
def __call__(self, secs):
with self._condition:
self._aborted = False
self._condition.wait(timeout=secs)
return not self._aborted
def abort(self):
with self._condition:
self._condition.notify()
self._aborted = True
I'd then also supply a Thread subclass to manage the sharing of the wakeup routine on a per-thread basis:
class ThreadWithWakeup(threading.Thread):
def __init__(self, *args, **kwargs):
self.abortable_sleep = AbortableSleep()
super(ThreadWithWakeup, self).__init__(*args, **kwargs)
def wakeup(self):
self.abortable_sleep.abort()
Any other thread with access to this thread can call wakeup() to abort the current abortable_sleep() (if one is in progress).
Using ThreadWithWakeup
You can create threads using the ThreadWithWakeup class, and use it like this:
class MyThread(ThreadWithWakeup):
def run(self):
print "Sleeper: sleeping for 10"
if self.abortable_sleep(10):
print "Sleeper: awoke naturally"
else:
print "Sleeper: rudely awoken"
t = MyThread()
t.start()
print "Main: sleeping for 5"
for i in range(5):
time.sleep(1)
print i + 1
print "Main: waking thread"
t.wakeup()
The output of which looks like:
Sleeper: sleeping for 10
Main: sleeping for 5
1
2
3
4
5
Main: waking thread
Sleeper: rudely awoken
Using AbortableSleep on its own
You can also use the AbortableSleep class on its own, which is handy if you can't use the ThreadWithWakeup class for some reason (maybe you're in the main thread, maybe something else creates the threads for you, etc.):
abortable_sleep = AbortableSleep()
def run():
print "Sleeper: sleeping for 10"
if abortable_sleep(10):
print "Sleeper: awoke naturally"
else:
print "Sleeper: rudely awoken"
threading.Thread(target=run).start()
print "Main: sleeping for 5"
for i in range(5):
time.sleep(1)
print i + 1
print "Main: aborting"
abortable_sleep.abort()
For threading.Timer Object, is there any way to update the timer time after calling start method ?
for example
timer = threading.Timer(5, function)
timer.start()
#after calling start method, i want to extend the timer time before expired.
as i looked through the document of threading.Timer, there isn't way.
so do i have to call cancel method then call again start method?
The Timer object is really quite simple:
def Timer(*args, **kwargs):
return _Timer(*args, **kwargs)
class _Timer(Thread):
"""Call a function after a specified number of seconds:
t = Timer(30.0, f, args=[], kwargs={})
t.start()
t.cancel() # stop the timer's action if it's still waiting
"""
def __init__(self, interval, function, args=[], kwargs={}):
Thread.__init__(self)
self.interval = interval
self.function = function
self.args = args
self.kwargs = kwargs
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()
It's just waiting calling wait with a timeout on a threading.Event object, then either runs the provided method or exits if cancel was called. You could implement your own version of Timer that supports extending the wait, but the default one definitely doesn't support it.
Nobody posted any code examples, so figure I might as well. Here I did as suggested as above where the timer is cancelled and then restarted. Using this solution will at first cause "hello world" to print every 5 seconds, and then on a rerun will increase that to every second in frequency. It also prints some Epoch times to demonstrate concurrency
import time
import threading
def printit(runs):
if runs == 1:
timer = threading.Timer(5.0, printit, [runs])
timer.start()
runs += 1
else:
timer = threading.Timer(1.0, printit, [runs])
timer.start()
print("Hello, World!")
timer.cancel()
timer = threading.Timer(1.0, printit, [runs])
timer.start()
if __name__ == '__main__':
runs = 1
printit(runs)
now = time.time()
print('The current time is: ' + str(now))
time.sleep(7)
current = time.time()
print('The current time is: ' + str(current))
Cancel the timer and start a new one.
I have recently posted a question about how to postpone execution of a function in Python (kind of equivalent to Javascript setTimeout) and it turns out to be a simple task using threading.Timer (well, simple as long as the function does not share state with other code, but that would create problems in any event-driven environment).
Now I am trying to do better and emulate setInterval. For those who are not familiar with Javascript, setInterval allows to repeat a call to a function every x seconds, without blocking the execution of other code. I have created this example decorator:
import time, threading
def setInterval(interval, times = -1):
# This will be the actual decorator,
# with fixed interval and times parameter
def outer_wrap(function):
# This will be the function to be
# called
def wrap(*args, **kwargs):
# This is another function to be executed
# in a different thread to simulate setInterval
def inner_wrap():
i = 0
while i != times:
time.sleep(interval)
function(*args, **kwargs)
i += 1
threading.Timer(0, inner_wrap).start()
return wrap
return outer_wrap
to be used as follows
#setInterval(1, 3)
def foo(a):
print(a)
foo('bar')
# Will print 'bar' 3 times with 1 second delays
and it seems to me it is working fine. My problem is that
it seems overly complicated, and I fear I may have missed a simpler/better mechanism
the decorator can be called without the second parameter, in which case it will go on forever. When I say foreover, I mean forever - even calling sys.exit() from the main thread will not stop it, nor will hitting Ctrl+c. The only way to stop it is to kill python process from the outside. I would like to be able to send a signal from the main thread that would stop the callback. But I am a beginner with threads - how can I communicate between them?
EDIT In case anyone wonders, this is the final version of the decorator, thanks to the help of jd
import threading
def setInterval(interval, times = -1):
# This will be the actual decorator,
# with fixed interval and times parameter
def outer_wrap(function):
# This will be the function to be
# called
def wrap(*args, **kwargs):
stop = threading.Event()
# This is another function to be executed
# in a different thread to simulate setInterval
def inner_wrap():
i = 0
while i != times and not stop.isSet():
stop.wait(interval)
function(*args, **kwargs)
i += 1
t = threading.Timer(0, inner_wrap)
t.daemon = True
t.start()
return stop
return wrap
return outer_wrap
It can be used with a fixed amount of repetitions as above
#setInterval(1, 3)
def foo(a):
print(a)
foo('bar')
# Will print 'bar' 3 times with 1 second delays
or can be left to run until it receives a stop signal
import time
#setInterval(1)
def foo(a):
print(a)
stopper = foo('bar')
time.sleep(5)
stopper.set()
# It will stop here, after printing 'bar' 5 times.
Your solution looks fine to me.
There are several ways to communicate with threads. To order a thread to stop, you can use threading.Event(), which has a wait() method that you can use instead of time.sleep().
stop_event = threading.Event()
...
stop_event.wait(1.)
if stop_event.isSet():
return
...
For your thread to exit when the program is terminated, set its daemon attribute to True before calling start(). This applies to Timer() objects as well because they subclass threading.Thread. See http://docs.python.org/library/threading.html#threading.Thread.daemon
Maybe these are the easiest setInterval equivalent in python:
import threading
def set_interval(func, sec):
def func_wrapper():
set_interval(func, sec)
func()
t = threading.Timer(sec, func_wrapper)
t.start()
return t
Maybe a bit simpler is to use recursive calls to Timer:
from threading import Timer
import atexit
class Repeat(object):
count = 0
#staticmethod
def repeat(rep, delay, func):
"repeat func rep times with a delay given in seconds"
if Repeat.count < rep:
# call func, you might want to add args here
func()
Repeat.count += 1
# setup a timer which calls repeat recursively
# again, if you need args for func, you have to add them here
timer = Timer(delay, Repeat.repeat, (rep, delay, func))
# register timer.cancel to stop the timer when you exit the interpreter
atexit.register(timer.cancel)
timer.start()
def foo():
print "bar"
Repeat.repeat(3,2,foo)
atexit allows to signal stopping with CTRL-C.
this class Interval
class ali:
def __init__(self):
self.sure = True;
def aliv(self,func,san):
print "ali naber";
self.setInterVal(func, san);
def setInterVal(self,func, san):
# istenilen saniye veya dakika aralığında program calışır.
def func_Calistir():
func(func,san); #calışıcak fonksiyon.
self.t = threading.Timer(san, func_Calistir)
self.t.start()
return self.t
a = ali();
a.setInterVal(a.aliv,5);
Does Python have a function similar to JavaScript's setInterval()?
I would like to have:
def set_interval(func, interval):
...
That will call func every interval time units.
This might be the correct snippet you were looking for:
import threading
def set_interval(func, sec):
def func_wrapper():
set_interval(func, sec)
func()
t = threading.Timer(sec, func_wrapper)
t.start()
return t
This is a version where you could start and stop.
It is not blocking.
There is also no glitch as execution time error is not added (important for long time execution with very short interval as audio for example)
import time, threading
StartTime=time.time()
def action() :
print('action ! -> time : {:.1f}s'.format(time.time()-StartTime))
class setInterval :
def __init__(self,interval,action) :
self.interval=interval
self.action=action
self.stopEvent=threading.Event()
thread=threading.Thread(target=self.__setInterval)
thread.start()
def __setInterval(self) :
nextTime=time.time()+self.interval
while not self.stopEvent.wait(nextTime-time.time()) :
nextTime+=self.interval
self.action()
def cancel(self) :
self.stopEvent.set()
# start action every 0.6s
inter=setInterval(0.6,action)
print('just after setInterval -> time : {:.1f}s'.format(time.time()-StartTime))
# will stop interval in 5s
t=threading.Timer(5,inter.cancel)
t.start()
Output is :
just after setInterval -> time : 0.0s
action ! -> time : 0.6s
action ! -> time : 1.2s
action ! -> time : 1.8s
action ! -> time : 2.4s
action ! -> time : 3.0s
action ! -> time : 3.6s
action ! -> time : 4.2s
action ! -> time : 4.8s
Just keep it nice and simple.
import threading
def setInterval(func,time):
e = threading.Event()
while not e.wait(time):
func()
def foo():
print "hello"
# using
setInterval(foo,5)
# output:
hello
hello
.
.
.
EDIT : This code is non-blocking
import threading
class ThreadJob(threading.Thread):
def __init__(self,callback,event,interval):
'''runs the callback function after interval seconds
:param callback: callback function to invoke
:param event: external event for controlling the update operation
:param interval: time in seconds after which are required to fire the callback
:type callback: function
:type interval: int
'''
self.callback = callback
self.event = event
self.interval = interval
super(ThreadJob,self).__init__()
def run(self):
while not self.event.wait(self.interval):
self.callback()
event = threading.Event()
def foo():
print "hello"
k = ThreadJob(foo,event,2)
k.start()
print "It is non-blocking"
Change Nailxx's answer a bit and you got the answer!
from threading import Timer
def hello():
print "hello, world"
Timer(30.0, hello).start()
Timer(30.0, hello).start() # after 30 seconds, "hello, world" will be printed
The sched module provides these abilities for general Python code. However, as its documentation suggests, if your code is multithreaded it might make more sense to use the threading.Timer class instead.
I think this is what you're after:
#timertest.py
import sched, time
def dostuff():
print "stuff is being done!"
s.enter(3, 1, dostuff, ())
s = sched.scheduler(time.time, time.sleep)
s.enter(3, 1, dostuff, ())
s.run()
If you add another entry to the scheduler at the end of the repeating method, it'll just keep going.
I use sched to create setInterval function gist
import functools
import sched, time
s = sched.scheduler(time.time, time.sleep)
def setInterval(sec):
def decorator(func):
#functools.wraps(func)
def wrapper(*argv, **kw):
setInterval(sec)(func)
func(*argv, **kw)
s.enter(sec, 1, wrapper, ())
return wrapper
s.run()
return decorator
#setInterval(sec=3)
def testInterval():
print ("test Interval ")
testInterval()
Simple setInterval utils
from threading import Timer
def setInterval(timer, task):
isStop = task()
if not isStop:
Timer(timer, setInterval, [timer, task]).start()
def hello():
print "do something"
return False # return True if you want to stop
if __name__ == "__main__":
setInterval(2.0, hello) # every 2 seconds, "do something" will be printed
The above method didn't quite do it for me as I needed to be able to cancel the interval. I turned the function into a class and came up with the following:
class setInterval():
def __init__(self, func, sec):
def func_wrapper():
self.t = threading.Timer(sec, func_wrapper)
self.t.start()
func()
self.t = threading.Timer(sec, func_wrapper)
self.t.start()
def cancel(self):
self.t.cancel()
Most of the answers above do not shut down the Thread properly. While using Jupyter notebook I noticed that when an explicit interrupt was sent, the threads were still running and worse, they would keep multiplying starting at 1 thread running,2, 4 etc. My method below is based on the answer by #doom but cleanly handles interrupts by running an infinite loop in the Main thread to listen for SIGINT and SIGTERM events
No drift
Cancelable
Handles SIGINT and SIGTERM very well
Doesnt make a new thread for every run
Feel free to suggest improvements
import time
import threading
import signal
# Record the time for the purposes of demonstration
start_time=time.time()
class ProgramKilled(Exception):
"""
An instance of this custom exception class will be thrown everytime we get an SIGTERM or SIGINT
"""
pass
# Raise the custom exception whenever SIGINT or SIGTERM is triggered
def signal_handler(signum, frame):
raise ProgramKilled
# This function serves as the callback triggered on every run of our IntervalThread
def action() :
print('action ! -> time : {:.1f}s'.format(time.time()-start_time))
# https://stackoverflow.com/questions/2697039/python-equivalent-of-setinterval
class IntervalThread(threading.Thread) :
def __init__(self,interval,action, *args, **kwargs) :
super(IntervalThread, self).__init__()
self.interval=interval
self.action=action
self.stopEvent=threading.Event()
self.start()
def run(self) :
nextTime=time.time()+self.interval
while not self.stopEvent.wait(nextTime-time.time()) :
nextTime+=self.interval
self.action()
def cancel(self) :
self.stopEvent.set()
def main():
# Handle SIGINT and SIFTERM with the help of the callback function
signal.signal(signal.SIGTERM, signal_handler)
signal.signal(signal.SIGINT, signal_handler)
# start action every 1s
inter=IntervalThread(1,action)
print('just after setInterval -> time : {:.1f}s'.format(time.time()-start_time))
# will stop interval in 500s
t=threading.Timer(500,inter.cancel)
t.start()
# https://www.g-loaded.eu/2016/11/24/how-to-terminate-running-python-threads-using-signals/
while True:
try:
time.sleep(1)
except ProgramKilled:
print("Program killed: running cleanup code")
inter.cancel()
break
if __name__ == "__main__":
main()
In the above solutions if a situation arises where program is shutdown, there is no guarantee that it will shutdown gracefully,Its always recommended to shut a program via a soft kill, neither did most of them have a function to stop I found a nice article on medium written by Sankalp which solves both of these issues (run periodic tasks in python) refer the attached link to get a deeper insight.
In the below sample a library named signal is used to track the kill is soft kill or a hard kill
import threading, time, signal
from datetime import timedelta
WAIT_TIME_SECONDS = 1
class ProgramKilled(Exception):
pass
def foo():
print time.ctime()
def signal_handler(signum, frame):
raise ProgramKilled
class Job(threading.Thread):
def __init__(self, interval, execute, *args, **kwargs):
threading.Thread.__init__(self)
self.daemon = False
self.stopped = threading.Event()
self.interval = interval
self.execute = execute
self.args = args
self.kwargs = kwargs
def stop(self):
self.stopped.set()
self.join()
def run(self):
while not self.stopped.wait(self.interval.total_seconds()):
self.execute(*self.args, **self.kwargs)
if __name__ == "__main__":
signal.signal(signal.SIGTERM, signal_handler)
signal.signal(signal.SIGINT, signal_handler)
job = Job(interval=timedelta(seconds=WAIT_TIME_SECONDS), execute=foo)
job.start()
while True:
try:
time.sleep(1)
except ProgramKilled:
print "Program killed: running cleanup code"
job.stop()
break
#output
#Tue Oct 16 17:47:51 2018
#Tue Oct 16 17:47:52 2018
#Tue Oct 16 17:47:53 2018
#^CProgram killed: running cleanup code
setInterval should be run on multiple thread, and not freeze the task when it running loop.
Here is my RUNTIME package that support multithread feature:
setTimeout(F,ms) : timming to fire function in independence thread.
delayF(F,ms) : similar setTimeout(F,ms).
setInterval(F,ms) : asynchronous loop
.pause, .resume : pause and resume the interval
clearInterval(interval) : clear the interval
It's short and simple. Note that python need lambda if you input direct the function, but lambda is not support command block, so you should define the function content before put it in the setInterval.
### DEMO PYTHON MULTITHREAD ASYNCHRONOUS LOOP ###
import time;
import threading;
import random;
def delay(ms):time.sleep(ms/1000); # Controil while speed
def setTimeout(R,delayMS):
t=threading.Timer(delayMS/1000,R)
t.start();
return t;
def delayF(R,delayMS):
t=threading.Timer(delayMS/1000,R)
t.start();
return t;
class THREAD:
def __init__(this):
this.R_onRun=None;
this.thread=None;
def run(this):
this.thread=threading.Thread(target=this.R_onRun);
this.thread.start();
def isRun(this): return this.thread.isAlive();
class setInterval :
def __init__(this,R_onRun,msInterval) :
this.ms=msInterval;
this.R_onRun=R_onRun;
this.kStop=False;
this.thread=THREAD();
this.thread.R_onRun=this.Clock;
this.thread.run();
def Clock(this) :
while not this.kStop :
this.R_onRun();
delay(this.ms);
def pause(this) :
this.kStop=True;
def stop(this) :
this.kStop=True;
def resume(this) :
if (this.kStop) :
this.kStop=False;
this.thread.run();
def clearInterval(Timer): Timer.stop();
# EXAMPLE
def p():print(random.random());
tm=setInterval(p,20);
tm2=setInterval(lambda:print("AAAAA"),20);
delayF(tm.pause,1000);
delayF(tm.resume,2000);
delayF(lambda:clearInterval(tm),3000);
Save to file .py and run it. You will see it print both random number and string "AAAAA". The print number thread will pause printing after 1 second and resume print again for 1 second then stop, while the print string keep printing text not corrupt.
In case you use OpenCV for graphic animation with those setInterval for boost animate speed, you must have 1 main thread to apply waitKey, otherwise the window will freeze no matter how slow delay or you applied waitKey in sub thread:
def p:... # Your drawing task
setInterval(p,1); # Subthread1 running draw
setInterval(p,1); # Subthread2 running draw
setInterval(p,1); # Subthread3 running draw
while True: cv2.waitKey(10); # Main thread which waitKey have effect
You can also try out this method:
import time
while True:
time.sleep(5)
print("5 seconds has passed")
So it will print "5 seconds has passed" every 5 seconds.
The function sleep() suspends execution for the given number of seconds. The argument may be a floating point number to indicate a more precise sleep time.
Recently, I have the same issue as you. And I find these soluation:
1. you can use the library: threading.Time(this have introduction above)
2. you can use the library: sched(this have introduction above too)
3. you can use the library: Advanced Python Scheduler(Recommend)
Some answers above that uses func_wrapper and threading.Timer indeed work, except that it spawns a new thread every time an interval is called, which is causing memory problems.
The basic example below roughly implemented a similar mechanism by putting interval on a separate thread. It sleeps at the given interval. Before jumping into code, here are some of the limitations that you need to be aware of:
JavaScript is single threaded, so when the function inside setInterval is fired, nothing else will be working at the same time (excluding worker thread, but let's talk general use case of setInterval. Therefore, threading is safe. But here in this implementation, you may encounter race conditions unless using a threading.rLock.
The implementation below uses time.sleep to simulate intervals, but adding the execution time of func, the total time for this interval may be greater than what you expect. So depending on use cases, you may want to "sleep less" (minus time taken for calling func)
I only roughly tested this, and you should definitely not use global variables the way I did, feel free to tweak it so that it fits in your system.
Enough talking, here is the code:
# Python 2.7
import threading
import time
class Interval(object):
def __init__(self):
self.daemon_alive = True
self.thread = None # keep a reference to the thread so that we can "join"
def ticktock(self, interval, func):
while self.daemon_alive:
time.sleep(interval)
func()
num = 0
def print_num():
global num
num += 1
print 'num + 1 = ', num
def print_negative_num():
global num
print '-num = ', num * -1
intervals = {} # keep track of intervals
g_id_counter = 0 # roughly generate ids for intervals
def set_interval(interval, func):
global g_id_counter
interval_obj = Interval()
# Put this interval on a new thread
t = threading.Thread(target=interval_obj.ticktock, args=(interval, func))
t.setDaemon(True)
interval_obj.thread = t
t.start()
# Register this interval so that we can clear it later
# using roughly generated id
interval_id = g_id_counter
g_id_counter += 1
intervals[interval_id] = interval_obj
# return interval id like it does in JavaScript
return interval_id
def clear_interval(interval_id):
# terminate this interval's while loop
intervals[interval_id].daemon_alive = False
# kill the thread
intervals[interval_id].thread.join()
# pop out the interval from registry for reusing
intervals.pop(interval_id)
if __name__ == '__main__':
num_interval = set_interval(1, print_num)
neg_interval = set_interval(3, print_negative_num)
time.sleep(10) # Sleep 10 seconds on main thread to let interval run
clear_interval(num_interval)
clear_interval(neg_interval)
print "- Are intervals all cleared?"
time.sleep(3) # check if both intervals are stopped (not printing)
print "- Yup, time to get beers"
Expected output:
num + 1 = 1
num + 1 = 2
-num = -2
num + 1 = 3
num + 1 = 4
num + 1 = 5
-num = -5
num + 1 = 6
num + 1 = 7
num + 1 = 8
-num = -8
num + 1 = 9
num + 1 = 10
-num = -10
Are intervals all cleared?
Yup, time to get beers
My Python 3 module jsinterval.py will be helpful! Here it is:
"""
Threaded intervals and timeouts from JavaScript
"""
import threading, sys
__all__ = ['TIMEOUTS', 'INTERVALS', 'setInterval', 'clearInterval', 'setTimeout', 'clearTimeout']
TIMEOUTS = {}
INTERVALS = {}
last_timeout_id = 0
last_interval_id = 0
class Timeout:
"""Class for all timeouts."""
def __init__(self, func, timeout):
global last_timeout_id
last_timeout_id += 1
self.timeout_id = last_timeout_id
TIMEOUTS[str(self.timeout_id)] = self
self.func = func
self.timeout = timeout
self.threadname = 'Timeout #%s' %self.timeout_id
def run(self):
func = self.func
delx = self.__del__
def func_wrapper():
func()
delx()
self.t = threading.Timer(self.timeout/1000, func_wrapper)
self.t.name = self.threadname
self.t.start()
def __repr__(self):
return '<JS Timeout set for %s seconds, launching function %s on timeout reached>' %(self.timeout, repr(self.func))
def __del__(self):
self.t.cancel()
class Interval:
"""Class for all intervals."""
def __init__(self, func, interval):
global last_interval_id
self.interval_id = last_interval_id
INTERVALS[str(self.interval_id)] = self
last_interval_id += 1
self.func = func
self.interval = interval
self.threadname = 'Interval #%s' %self.interval_id
def run(self):
func = self.func
interval = self.interval
def func_wrapper():
timeout = Timeout(func_wrapper, interval)
self.timeout = timeout
timeout.run()
func()
self.t = threading.Timer(self.interval/1000, func_wrapper)
self.t.name = self.threadname
self.t.run()
def __repr__(self):
return '<JS Interval, repeating function %s with interval %s>' %(repr(self.func), self.interval)
def __del__(self):
self.timeout.__del__()
def setInterval(func, interval):
"""
Create a JS Interval: func is the function to repeat, interval is the interval (in ms)
of executing the function.
"""
temp = Interval(func, interval)
temp.run()
idx = int(temp.interval_id)
del temp
return idx
def clearInterval(interval_id):
try:
INTERVALS[str(interval_id)].__del__()
del INTERVALS[str(interval_id)]
except KeyError:
sys.stderr.write('No such interval "Interval #%s"\n' %interval_id)
def setTimeout(func, timeout):
"""
Create a JS Timeout: func is the function to timeout, timeout is the timeout (in ms)
of executing the function.
"""
temp = Timeout(func, timeout)
temp.run()
idx = int(temp.timeout_id)
del temp
return idx
def clearTimeout(timeout_id):
try:
TIMEOUTS[str(timeout_id)].__del__()
del TIMEOUTS[str(timeout_id)]
except KeyError:
sys.stderr.write('No such timeout "Timeout #%s"\n' %timeout_id)
CODE EDIT:
Fixed the memory leak (spotted by #benjaminz). Now ALL threads are cleaned up upon end. Why does this leak happen? It happens because of the implicit (or even explicit) references. In my case, TIMEOUTS and INTERVALS. Timeouts self-clean automatically (after this patch) because they use function wrapper which calls the function and then self-kills. But how does this happen? Objects can't be deleted from memory unless all references are deleted too or gc module is used. Explaining: there's no way to create (in my code) unwanted references to timeouts/intervals. They have only ONE referrer: the TIMEOUTS/INTERVALS dicts. And, when interrupted or finished (only timeouts can finish uninterrupted) they delete the only existing reference to themselves: their corresponding dict element. Classes are perfectly encapsulated using __all__, so no space for memory leaks.
Here is a low time drift solution that uses a thread to periodically signal an Event object. The thread's run() does almost nothing while waiting for a timeout; hence the low time drift.
# Example of low drift (time) periodic execution of a function.
import threading
import time
# Thread that sets 'flag' after 'timeout'
class timerThread (threading.Thread):
def __init__(self , timeout , flag):
threading.Thread.__init__(self)
self.timeout = timeout
self.stopFlag = False
self.event = threading.Event()
self.flag = flag
# Low drift run(); there is only the 'if'
# and 'set' methods between waits.
def run(self):
while not self.event.wait(self.timeout):
if self.stopFlag:
break
self.flag.set()
def stop(self):
stopFlag = True
self.event.set()
# Data.
printCnt = 0
# Flag to print.
printFlag = threading.Event()
# Create and start the timer thread.
printThread = timerThread(3 , printFlag)
printThread.start()
# Loop to wait for flag and print time.
while True:
global printCnt
# Wait for flag.
printFlag.wait()
# Flag must be manually cleared.
printFlag.clear()
print(time.time())
printCnt += 1
if printCnt == 3:
break;
# Stop the thread and exit.
printThread.stop()
printThread.join()
print('Done')
fall asleep until the next interval of seconds length starts: (not concurrent)
def sleep_until_next_interval(self, seconds):
now = time.time()
fall_asleep = seconds - now % seconds
time.sleep(fall_asleep)
while True:
sleep_until_next_interval(10) # 10 seconds - worktime
# work here
simple and no drift.
I have written my code to make a very very flexible setInterval in python. Here you are:
import threading
class AlreadyRunning(Exception):
pass
class IntervalNotValid(Exception):
pass
class setInterval():
def __init__(this, func=None, sec=None, args=[]):
this.running = False
this.func = func # the function to be run
this.sec = sec # interval in second
this.Return = None # The returned data
this.args = args
this.runOnce = None # asociated with run_once() method
this.runOnceArgs = None # asociated with run_once() method
if (func is not None and sec is not None):
this.running = True
if (not callable(func)):
raise TypeError("non-callable object is given")
if (not isinstance(sec, int) and not isinstance(sec, float)):
raise TypeError("A non-numeric object is given")
this.TIMER = threading.Timer(this.sec, this.loop)
this.TIMER.start()
def start(this):
if (not this.running):
if (not this.isValid()):
raise IntervalNotValid("The function and/or the " +
"interval hasn't provided or invalid.")
this.running = True
this.TIMER = threading.Timer(this.sec, this.loop)
this.TIMER.start()
else:
raise AlreadyRunning("Tried to run an already run interval")
def stop(this):
this.running = False
def isValid(this):
if (not callable(this.func)):
return False
cond1 = not isinstance(this.sec, int)
cond2 = not isinstance(this.sec, float)
if (cond1 and cond2):
return False
return True
def loop(this):
if (this.running):
this.TIMER = threading.Timer(this.sec, this.loop)
this.TIMER.start()
function_, Args_ = this.func, this.args
if (this.runOnce is not None): # someone has provide the run_once
runOnce, this.runOnce = this.runOnce, None
result = runOnce(*(this.runOnceArgs))
this.runOnceArgs = None
# if and only if the result is False. not accept "None"
# nor zero.
if (result is False):
return # cancel the interval right now
this.Return = function_(*Args_)
def change_interval(this, sec):
cond1 = not isinstance(sec, int)
cond2 = not isinstance(sec, float)
if (cond1 and cond2):
raise TypeError("A non-numeric object is given")
# prevent error when providing interval to a blueprint
if (this.running):
this.TIMER.cancel()
this.sec = sec
# prevent error when providing interval to a blueprint
# if the function hasn't provided yet
if (this.running):
this.TIMER = threading.Timer(this.sec, this.loop)
this.TIMER.start()
def change_next_interval(this, sec):
if (not isinstance(sec, int) and not isinstance(sec, float)):
raise TypeError("A non-numeric object is given")
this.sec = sec
def change_func(this, func, args=[]):
if (not callable(func)):
raise TypeError("non-callable object is given")
this.func = func
this.args = args
def run_once(this, func, args=[]):
this.runOnce = func
this.runOnceArgs = args
def get_return(this):
return this.Return
You can get many features and flexibility. Running this code won't freeze your code, you can change the interval at run time, you can change the function at run time, you can pass arguments, you can get the returned object from your function, and many more. You can make your tricks too!
here's a very simple and basic example to use it:
import time
def interval(name="world"):
print(f"Hello {name}!")
# function named interval will be called every two seconds
# output: "Hello world!"
interval1 = setInterval(interval, 2)
# function named interval will be called every 1.5 seconds
# output: "Hello Jane!"
interval2 = setInterval(interval, 1.5, ["Jane"])
time.sleep(5) #stop all intervals after 5 seconds
interval1.stop()
interval2.stop()
Check out my Github project to see more examples and follow next updates :D
https://github.com/Hzzkygcs/setInterval-python
Here's something easy peazy:
import time
delay = 10 # Seconds
def setInterval():
print('I print in intervals!')
time.sleep(delay)
setInterval()
Things work differently in Python: you need to either sleep() (if you want to block the current thread) or start a new thread. See http://docs.python.org/library/threading.html
From Python Documentation:
from threading import Timer
def hello():
print "hello, world"
t = Timer(30.0, hello)
t.start() # after 30 seconds, "hello, world" will be printed