Question

我有这个装饰者：

def timed_out(timeout):
    def decorate(f):
        if not hasattr(signal, "SIGALRM"):
            return f

        def handler(signum, frame):
            raise TimedOutExc()

        @functools.wraps(f)
        def new_f(*args, **kwargs):
            old = signal.signal(signal.SIGALRM, handler)
            signal.alarm(timeout)
            try:
                result = f(*args, **kwargs)
            finally:
                signal.signal(signal.SIGALRM, old)
            signal.alarm(0)
            return result

        new_f.func_name = f.func_name
        return new_f

    return decorate

代码只能在linux上执行任何操作，但在Windows上，没有SIGALRM。在Windows中使用此代码的最简单方法是什么？

Answer 1

它不是很漂亮，但我必须以跨平台的方式做类似的事情，我想出了一个单独的线程。基于信号的系统无法可靠地在所有平台上运行。

此类的使用可以包含在装饰器中，也可以制作成with上下文处理程序。

因人而异。

#!/usr/bin/env python2.7
import time, threading

class Ticker(threading.Thread):
  """A very simple thread that merely blocks for :attr:`interval` and sets a
  :class:`threading.Event` when the :attr:`interval` has elapsed. It then waits
  for the caller to unset this event before looping again.

  Example use::

    t = Ticker(1.0) # make a ticker
    t.start() # start the ticker in a new thread
    try:
      while t.evt.wait(): # hang out til the time has elapsed
        t.evt.clear() # tell the ticker to loop again
        print time.time(), "FIRING!"
    except:
      t.stop() # tell the thread to stop
      t.join() # wait til the thread actually dies

  """
  # SIGALRM based timing proved to be unreliable on various python installs,
  # so we use a simple thread that blocks on sleep and sets a threading.Event
  # when the timer expires, it does this forever.
  def __init__(self, interval):
    super(Ticker, self).__init__()
    self.interval = interval
    self.evt = threading.Event()
    self.evt.clear()
    self.should_run = threading.Event()
    self.should_run.set()

  def stop(self):
    """Stop the this thread. You probably want to call :meth:`join` immediately
    afterwards
    """
    self.should_run.clear()

  def consume(self):
    was_set = self.evt.is_set()
    if was_set:
      self.evt.clear()
    return was_set

  def run(self):
    """The internal main method of this thread. Block for :attr:`interval`
    seconds before setting :attr:`Ticker.evt`

    .. warning::
      Do not call this directly!  Instead call :meth:`start`.
    """
    while self.should_run.is_set():
      time.sleep(self.interval)
      self.evt.set()

Answer 2

我发现这个超时装饰器代码也非常方便。（我最初在这个问题答案中找到了它：How to limit execution time of a function call in Python）

为了使它在Windows上运行，我使用与Cygwin一起安装的Python。

我运行setup-x86_64.exe，然后从Python文件夹中选择python3包。（或者，如果您更喜欢Python 2，python包。）

要将python3重命名为python2，我定义了别名

alias python=python3

从Cygwin命令提示符

。由于我不常使用此功能，我可能不会将其放入.bashrc或其他任何内容。

相关问题： Python signal don't work even on Cygwin?

python：相当于SIGALRM的windows

2 个答案: