diff options
Diffstat (limited to 'Lib/sched.py')
| -rw-r--r-- | Lib/sched.py | 31 |
1 files changed, 21 insertions, 10 deletions
diff --git a/Lib/sched.py b/Lib/sched.py index 2b599ee..2f8df05 100644 --- a/Lib/sched.py +++ b/Lib/sched.py @@ -15,7 +15,7 @@ integers or floating point numbers, as long as it is consistent. Events are specified by tuples (time, priority, action, argument). As in UNIX, lower priority numbers mean higher priority; in this -way the queue can be maintained fully sorted. Execution of the +way the queue can be maintained as a priority queue. Execution of the event means calling the action function, passing it the argument. Remember that in Python, multiple function arguments can be packed in a tuple. The action function may be an instance method so it @@ -28,7 +28,7 @@ Parameterless functions or methods cannot be used, however. # XXX instead of having to define a module or class just to hold # XXX the global state of your particular time and delay functions. -import bisect +import heapq __all__ = ["scheduler"] @@ -48,7 +48,7 @@ class scheduler: """ event = time, priority, action, argument - bisect.insort(self.queue, event) + heapq.heappush(self.queue, event) return event # The ID def enter(self, delay, priority, action, argument): @@ -68,10 +68,11 @@ class scheduler: """ self.queue.remove(event) + heapq.heapify(self.queue) def empty(self): """Check whether the queue is empty.""" - return len(self.queue) == 0 + return not not self.queue def run(self): """Execute events until the queue is empty. @@ -94,13 +95,23 @@ class scheduler: runnable. """ + # localize variable access to minimize overhead + # and to improve thread safety q = self.queue + delayfunc = self.delayfunc + timefunc = self.timefunc + pop = heapq.heappop while q: - time, priority, action, argument = q[0] - now = self.timefunc() + time, priority, action, argument = checked_event = q[0] + now = timefunc() if now < time: - self.delayfunc(time - now) + delayfunc(time - now) else: - del q[0] - void = action(*argument) - self.delayfunc(0) # Let other threads run + event = pop(q) + # Verify that the event was not removed or altered + # by another thread after we last looked at q[0]. + if event is checked_event: + void = action(*argument) + delayfunc(0) # Let other threads run + else: + heapq.heappush(event) |