diff options
Diffstat (limited to 'Lib/sched.py')
| -rw-r--r-- | Lib/sched.py | 45 |
1 files changed, 31 insertions, 14 deletions
diff --git a/Lib/sched.py b/Lib/sched.py index 1643236..f0da829 100644 --- a/Lib/sched.py +++ b/Lib/sched.py @@ -16,11 +16,11 @@ 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 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 +event means calling the action function, passing it the argument +sequence in "argument" (remember that in Python, multiple function +arguments are be packed in a sequence). +The action function may be an instance method so it has another way to reference private data (besides global variables). -Parameterless functions or methods cannot be used, however. """ # XXX The timefunc and delayfunc should have been defined as methods @@ -29,14 +29,17 @@ Parameterless functions or methods cannot be used, however. # XXX the global state of your particular time and delay functions. import heapq +from collections import namedtuple __all__ = ["scheduler"] +Event = namedtuple('Event', 'time, priority, action, argument') + class scheduler: def __init__(self, timefunc, delayfunc): """Initialize a new instance, passing the time and delay functions""" - self.queue = [] + self._queue = [] self.timefunc = timefunc self.delayfunc = delayfunc @@ -47,8 +50,8 @@ class scheduler: if necessary. """ - event = time, priority, action, argument - heapq.heappush(self.queue, event) + event = Event(time, priority, action, argument) + heapq.heappush(self._queue, event) return event # The ID def enter(self, delay, priority, action, argument): @@ -64,15 +67,15 @@ class scheduler: """Remove an event from the queue. This must be presented the ID as returned by enter(). - If the event is not in the queue, this raises RuntimeError. + If the event is not in the queue, this raises ValueError. """ - self.queue.remove(event) - heapq.heapify(self.queue) + self._queue.remove(event) + heapq.heapify(self._queue) def empty(self): """Check whether the queue is empty.""" - return not self.queue + return not self._queue def run(self): """Execute events until the queue is empty. @@ -89,7 +92,7 @@ class scheduler: exceptions are not caught but the scheduler's state remains well-defined so run() may be called again. - A questionably hack is added to allow other threads to run: + A questionable hack is added to allow other threads to run: just after an event is executed, a delay of 0 is executed, to avoid monopolizing the CPU when other threads are also runnable. @@ -97,7 +100,7 @@ class scheduler: """ # localize variable access to minimize overhead # and to improve thread safety - q = self.queue + q = self._queue delayfunc = self.delayfunc timefunc = self.timefunc pop = heapq.heappop @@ -111,7 +114,21 @@ class scheduler: # 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) + action(*argument) delayfunc(0) # Let other threads run else: heapq.heappush(q, event) + + @property + def queue(self): + """An ordered list of upcoming events. + + Events are named tuples with fields for: + time, priority, action, arguments + + """ + # Use heapq to sort the queue rather than using 'sorted(self._queue)'. + # With heapq, two events scheduled at the same time will show in + # the actual order they would be retrieved. + events = self._queue[:] + return map(heapq.heappop, [events]*len(events)) |