python等效于setInterval（）？

Question

Python的功能与JavaScript类似 setInterval()?

谢谢

Answer 1

这可能是您要寻找的正确片段：

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

Answer 2

只要保持良好而简单。

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
.
.
.

编辑：此代码是非障碍物

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"

Answer 3

这是您可以开始和停止的版本。它没有阻止。由于没有添加执行时间错误，因此也没有故障（对于长时间执行至关重要，例如音频的时间很短）

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()

输出为：

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

Answer 4

改变 Nailxx回答一点，您得到了答案！

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

Answer 5

这 sched 模块为一般Python代码提供了这些能力。但是，正如其文档所暗示的那样，如果您的代码是多线程，则使用该代码可能更有意义 threading.Timer 课堂。

Answer 6

我认为这就是您所追求的：

#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()

如果在重复方法的末尾向调度程序添加另一个条目，它将继续进行。

Answer 7

简单的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

Answer 8

最近，我和您有同样的问题。我发现这些解决方案：

1.您可以使用库： 螺纹。时间（上面有介绍）

2.您可以使用库： 计划（这也有上面的介绍）

3.您可以使用库： 高级Python调度程序（推荐）

Answer 9

上面的方法对我来说并没有完全做到这一点，因为我需要能够取消间隔。我将功能变成了一堂课，并提出了以下内容：

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()

Answer 10

上面的一些答案使用 func_wrapper 和 threading.Timer 确实有效，除了每次调用间隔时都会产生一个新线程，这会导致内存问题。

下面的基本示例 大致 通过将间隔放在单独的线程上实现了类似的机制。它以给定的间隔睡觉。在加入代码之前，这里有一些您需要注意的局限性：

1. JavaScript是单线螺纹，因此当功能内部的功能 setInterval 被解雇了，没有其他任何事情同时工作（不包括工人线程，但让我们谈谈一般用例 setInterval. 。因此，线程是安全的。但是在此实施中，您可能会遇到种族条件，除非使用 threading.rLock.

2. 下面的实现使用 time.sleep 为了模拟间隔，但添加了执行时间 func, ，总时间 间隔 可能比您期望的要大。因此，根据用例，您可能想“少入睡”（拨打电话的时间减去 func)

3. 我只是 大致 对此进行了测试，您绝对不应该按照我的方式使用全局变量，可以随意调整它以使其适合您的系统。

---

说话足够，这是代码：

# 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"

预期输出：

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

Answer 11

我的python 3模块 jsinterval.py 会有所帮助！这里是：

"""
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)

---

代码编辑： 修复了内存泄漏（@Benjaminz发现）。现在，所有线程在结束时都被清理。为什么会发生这种泄漏？由于隐式（甚至是显式）引用而发生的。就我而 TIMEOUTS 和 INTERVALS. 。超时自动清洁（此补丁后），因为他们使用调用功能然后自杀的功能包装器。但是这是怎么发生的？除非所有引用也被删除，否则不能从内存中删除对象 gc 使用模块。解释：没有办法（在我的代码中）对超时/间隔的不需要引用。他们只有一个推荐人： TIMEOUTS/INTERVALS 命令。而且，当中断或完成（只有超时才能完成不间断）时，它们会删除对自己的唯一现有引用：相应的dict元素。课程完美地封装 __all__, ，因此没有用于内存泄漏的空间。

Answer 12

这是一个低时间漂移解决方案，它使用线程定期向事件对象发出信号。线程的运行（）在等待暂停时几乎什么都不做；因此，低时间漂移。

# 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')

Answer 13

上面的大多数答案不能正确关闭线程。在使用jupyter笔记本电脑时，我注意到当发送明显的中断时，线程仍在运行，更糟糕的是，它们会继续以1个线程运行，2、4等开始乘以乘法，我的方法是基于@doom的答案，但干净通过在主线程中运行无限循环来聆听Sigint和Sigterm事件来处理中断

• 没有漂移
• 可取消
• 处理Sigint和Sigment非常好
• 每次运行都不会有一个新线程

随时建议改进

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()

Answer 14

在Python中，情况有所不同：您需要 sleep() （如果要阻止当前线程）或启动新线程。看 http://docs.python.org/library/threading.html

Answer 15

从 Python文档:

from threading import Timer

def hello():
    print "hello, world"

t = Timer(30.0, hello)
t.start() # after 30 seconds, "hello, world" will be printed