例如,有没有办法每隔n秒打印一次Hello World!
?
例如,程序将通过我拥有的任何代码,然后一旦它有5秒(使用time.sleep()
)它将执行该代码。我会使用它来更新文件,而不是打印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
答案 0 :(得分:261)
import threading
def printit():
threading.Timer(5.0, printit).start()
print "Hello, World!"
printit()
# continue with the rest of your code
https://docs.python.org/3/library/threading.html#timer-objects
答案 1 :(得分:100)
我对这个主题的谦虚看法,对Alex Martelli答案的概括,以及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!
特点:
start()
和stop()
也可以安全地多次呼叫interval
,它会在下次运行后生效。 args
,kwargs
甚至function
!答案 2 :(得分:25)
保存自己的精神分裂症情节并使用Advanced Python调度程序: http://pythonhosted.org/APScheduler
代码很简单:
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()
答案 3 :(得分:20)
def update():
import time
while True:
print 'Hello World!'
time.sleep(5)
这将作为一个功能运行。 while True:
使它永远运行。如果需要,您可以随时将其从功能中取出。
答案 4 :(得分:13)
以下是与APScheduler 3.00+兼容的简单示例:
# 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,您可以使用以下内容。与许多替代方案不同,此计时器将每隔 n 秒执行所需的代码(无论代码执行的时间如何)。因此,如果您无法承受任何漂移,这是一个很好的选择。
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()
答案 5 :(得分:7)
这是一个每n
秒无法创建新主题的版本:
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
该事件用于停止重复:
cancel_future_calls = call_repeatedly(5, print, "Hello, World")
# do something else here...
cancel_future_calls() # stop future calls
答案 6 :(得分:1)
您可以启动一个单独的线程,其唯一职责是计数5秒,更新文件,重复。你不希望这个单独的线程干扰你的主线程。