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diff --git a/Doc/lib/libsched.tex b/Doc/lib/libsched.tex new file mode 100644 index 0000000..afa9c6f --- /dev/null +++ b/Doc/lib/libsched.tex @@ -0,0 +1,95 @@ +% LaTeXed and enhanced from comments in file +\section{\module{sched} --- + Event scheduler} + +\declaremodule{standard}{sched} +\sectionauthor{Moshe Zadka}{mzadka@geocities.com} +\modulesynopsis{General purpose event scheduler.} + +The \module{sched} module defines a class which implements a general +purpose event scheduler: + +\begin{classdesc}{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'' +--- \var{timefunc} should be callable without arguments, and return +a number (the ``time'', in any units whatsoever). The \var{delayfunc} +function should be callable with one argument, compatible with the output +of \var{timefunc}, and should delay that many time units. +\var{delayfunc} will also be called with the argument \code{0} after +each event is run to allow other threads an opportunity to run in +multi-threaded applications. +\end{classdesc} + +Example: + +\begin{verbatim} +>>> 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 +\end{verbatim} + + +\subsection{Schedule Objects \label{schedule-objects}} + +\class{schdule} instances have the following methods: + +\begin{methoddesc}{enterabs}{time, priority, action, argument} +Schedule a new event. The \var{time} argument should be a numeric type +compatible to the return value of \var{timefunc}. Events scheduled for +the same \var{time} will be executed in the order of their +\var{priority}. + +Executing the event means executing \code{apply(\var{action}, +\var{argument})}. \var{argument} must be a tuple holding the +parameters for \var{action}. + +Return value is an event which may be used for later cancellation of +the event (see \method{cancel()}). +\end{methoddesc} + +\begin{methoddesc}{enter}{delay, priority, action, argument} +Schedule an event for \var{delay} more time units. Other then the +relative time, the other arguments, the effect and the return value +are the same as those for \method{enterabs()}. +\end{methoddesc} + +\begin{methoddesc}{cancel}{event} +Remove the event from the queue. If \var{event} is not an event +currently in the queue, this method will raise a +\exception{RuntimeError}. +\end{methoddesc} + +\begin{methoddesc}{empty}{} +Check whether there are no scheduled events. +\end{methoddesc} + +\begin{methoddesc}{run}{} +Run all scheduled events. This function will wait +(using the \function{delayfunc} function passed to the constructor) +for the next event, then execute it and so on until there are no more +scheduled events. + +Either \var{action} or \var{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 \var{action}, +the event will not be attempted in future calls to \method{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 cancelling +events which are no longer pertinent. +\end{methoddesc} |