Question

抱歉这个老问题。我澄清了。如何用我糟糕的线程类启动一个停止线程？

编辑：它处于循环中，我想在代码的开头再次重启它。我怎么做start-stop-restart-stop-restart？

我的课程：

import threading

class Concur(threading.Thread):
    def __init__(self):
        self.stopped = False
        threading.Thread.__init__(self)

    def run(self):
        i = 0
        while not self.stopped:
            time.sleep(1)
            i = i + 1

在主要代码中，我想：

inst = Concur()

while conditon:
    inst.start()

    #after some operation
    inst.stop()
    #some other operation

Answer 1

您实际上无法停止然后重新启动线程，因为在start()方法终止后无法再次调用run()。但是，您可以通过使用threading.Condition变量使一个停止并稍后恢复执行，以避免在检查或更改其运行状态时出现并发问题。

Condition个对象具有关联的threading.Lock对象和方法，等待它被释放，并在发生时通知任何等待的线程。这是一个从您的问题中的代码派生的示例，它显示了这一点。在示例代码中，我将Condition变量作为Thread子类实例的一部分，以更好地封装实现，并避免需要引入其他全局变量：

from __future__ import print_function
import threading
import time

class Concur(threading.Thread):
    def __init__(self):
        super(Concur, self).__init__()
        self.iterations = 0
        self.daemon = True  # Allow main to exit even if still running.
        self.paused = True  # Start out paused.
        self.state = threading.Condition()

    def run(self):
        self.resume()
        while True:
            with self.state:
                if self.paused:
                    self.state.wait()  # Block execution until notified.
            # Do stuff.
            time.sleep(.1)
            self.iterations += 1

    def resume(self):
        with self.state:
            self.paused = False
            self.state.notify()  # Unblock self if waiting.

    def pause(self):
        with self.state:
            self.paused = True  # Block self.


class Stopwatch(object):
    """ Simple class to measure elapsed times. """
    def start(self):
        """ Establish reference point for elapsed time measurements. """
        self.start_time = time.time()
        return self.start_time

    @property
    def elapsed_time(self):
        """ Seconds since started. """
        try:
            start_time = self.start_time
        except AttributeError:  # Wasn't explicitly started.
            start_time = self.start()

        return time.time() - start_time


MAX_RUN_TIME = 5  # Seconds.
concur = Concur()
stopwatch = Stopwatch()

print('Running for {} seconds...'.format(MAX_RUN_TIME))
concur.start()
while stopwatch.elapsed_time < MAX_RUN_TIME:
    concur.resume()
    # ... do some concurrent operations.
    concur.pause()
    # Do some other stuff...

# Show Concur thread executed.
print('concur.iterations: {}'.format(concur.iterations))

Answer 2

这是David Heffernan的想法充实。下面的示例运行1秒钟，然后停止1秒钟，然后运行1秒钟，依此类推。

import time
import threading
import datetime as DT
import logging
logger = logging.getLogger(__name__)

def worker(cond):
    i = 0
    while True:
        with cond:
            cond.wait()
            logger.info(i)
            time.sleep(0.01)
            i += 1

logging.basicConfig(level=logging.DEBUG,
                    format='[%(asctime)s %(threadName)s] %(message)s',
                    datefmt='%H:%M:%S')

cond = threading.Condition()
t = threading.Thread(target=worker, args=(cond, ))
t.daemon = True
t.start()

start = DT.datetime.now()
while True:
    now = DT.datetime.now()
    if (now-start).total_seconds() > 60: break
    if now.second % 2:
        with cond:
            cond.notify()

Answer 3

stop()的实现如下所示：

def stop(self):
    self.stopped = True

如果要重新启动，则可以创建一个新实例并启动它。

while conditon:
    inst = Concur()
    inst.start()

    #after some operation
    inst.stop()
    #some other operation

Thread的{{3}}表明start()方法只能为每个类的实例调用一次。

如果您想暂停和恢复某个帖子，那么您需要使用documentation。

如何启动和停止线程？

3 个答案: