33 lines
1.3 KiB
Python
33 lines
1.3 KiB
Python
"""Version of sched.scheduler with a fixed cancel() method."""
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import heapq
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import sched
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class Scheduler(sched.scheduler):
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"""A thread-safe, general purpose event scheduler."""
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def cancel(self, event):
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"""Remove an event from the queue.
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Raises a ValueError if the event is not in the queue.
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"""
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# The changes from https://hg.python.org/cpython/rev/d8802b055474 made it so sched.Event
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# instances returned by sched.scheduler.enter() and sched.scheduler.enterabs() are treated
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# as equal if they have the same (time, priority). It is therefore possible to remove the
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# wrong event from the list when sched.scheduler.cancel() is called. Note that this is still
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# true even with time.monotonic being the default timefunc, as GetTickCount64() on Windows
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# only has a resolution of ~15ms. We therefore use the `is` operator to remove the correct
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# event from the list.
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with self._lock:
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# Disable warning, since we're deleting elements from a queue while traversing it
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# pylint: disable=C0200
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for i in range(len(self._queue)):
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if self._queue[i] is event:
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del self._queue[i]
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heapq.heapify(self._queue)
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return
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raise ValueError("event not in list")
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