python: windows equivalent of SIGALRM

It's not very pretty, but I had to do something similar in a cross-platform way, and I came up with using a separate thread. Signal based systems did not work on all platforms reliably.

Use of this class could be wrapped up in a decorator, or made into a with context handler.

YMMV.

#!/usr/bin/env python2.7import time, threadingclass 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()

This answer works only in Cygwin

I find this timeout-decorator code very handy, too. (I originally found it in this question answer: How to limit execution time of a function call?)

To make it work on Windows, I use the Python that is installed with Cygwin.

I run setup-x86_64.exe, then select the python3 package from the Python folder. (Or, if you prefer Python 2, the python package.)

To rename python3 to python2, I define the alias

alias python=python3

from the Cygwin command prompt. Since I don't use this functionality very often, I probably won't put it into a .bashrc or anything.

Related question:Python signal don't work even on Cygwin?