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author | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
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committer | Georg Brandl <georg@python.org> | 2007-08-15 14:28:22 (GMT) |
commit | 116aa62bf54a39697e25f21d6cf6799f7faa1349 (patch) | |
tree | 8db5729518ed4ca88e26f1e26cc8695151ca3eb3 /Doc/library/sched.rst | |
parent | 739c01d47b9118d04e5722333f0e6b4d0c8bdd9e (diff) | |
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Move the 3k reST doc tree in place.
Diffstat (limited to 'Doc/library/sched.rst')
-rw-r--r-- | Doc/library/sched.rst | 104 |
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diff --git a/Doc/library/sched.rst b/Doc/library/sched.rst new file mode 100644 index 0000000..bf3efbf --- /dev/null +++ b/Doc/library/sched.rst @@ -0,0 +1,104 @@ + +:mod:`sched` --- Event scheduler +================================ + +.. module:: sched + :synopsis: General purpose event scheduler. +.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il> + + +.. % LaTeXed and enhanced from comments in file + +.. index:: single: event scheduling + +The :mod:`sched` module defines a class which implements a general purpose event +scheduler: + + +.. class:: scheduler(timefunc, delayfunc) + + The :class:`scheduler` class defines a generic interface to scheduling events. + It needs two functions to actually deal with the "outside world" --- *timefunc* + should be callable without arguments, and return a number (the "time", in any + units whatsoever). The *delayfunc* function should be callable with one + argument, compatible with the output of *timefunc*, and should delay that many + time units. *delayfunc* will also be called with the argument ``0`` after each + event is run to allow other threads an opportunity to run in multi-threaded + applications. + +Example:: + + >>> import sched, time + >>> s=sched.scheduler(time.time, time.sleep) + >>> def print_time(): print "From print_time", time.time() + ... + >>> def print_some_times(): + ... print time.time() + ... s.enter(5, 1, print_time, ()) + ... s.enter(10, 1, print_time, ()) + ... s.run() + ... print time.time() + ... + >>> print_some_times() + 930343690.257 + From print_time 930343695.274 + From print_time 930343700.273 + 930343700.276 + + +.. _scheduler-objects: + +Scheduler Objects +----------------- + +:class:`scheduler` instances have the following methods: + + +.. method:: scheduler.enterabs(time, priority, action, argument) + + Schedule a new event. The *time* argument should be a numeric type compatible + with the return value of the *timefunc* function passed to the constructor. + Events scheduled for the same *time* will be executed in the order of their + *priority*. + + Executing the event means executing ``action(*argument)``. *argument* must be a + sequence holding the parameters for *action*. + + Return value is an event which may be used for later cancellation of the event + (see :meth:`cancel`). + + +.. method:: scheduler.enter(delay, priority, action, argument) + + Schedule an event for *delay* more time units. Other then the relative time, the + other arguments, the effect and the return value are the same as those for + :meth:`enterabs`. + + +.. method:: scheduler.cancel(event) + + Remove the event from the queue. If *event* is not an event currently in the + queue, this method will raise a :exc:`RuntimeError`. + + +.. method:: scheduler.empty() + + Return true if the event queue is empty. + + +.. method:: scheduler.run() + + Run all scheduled events. This function will wait (using the :func:`delayfunc` + function passed to the constructor) for the next event, then execute it and so + on until there are no more scheduled events. + + Either *action* or *delayfunc* can raise an exception. In either case, the + scheduler will maintain a consistent state and propagate the exception. If an + exception is raised by *action*, the event will not be attempted in future calls + to :meth:`run`. + + If a sequence of events takes longer to run than the time available before the + next event, the scheduler will simply fall behind. No events will be dropped; + the calling code is responsible for canceling events which are no longer + pertinent. + |