While we're at it, convert to docstrings and set the indentation level

to 4.
This commit is contained in:
Fred Drake 1999-06-25 18:53:23 +00:00
parent 7e990323b4
commit 5c4012adc0

View file

@ -1,91 +1,97 @@
# Module sched -- a generally useful event scheduler class """Module sched -- a generally useful event scheduler class
# Each instance of this class manages its own queue. Each instance of this class manages its own queue.
# No multi-threading is implied; you are supposed to hack that No multi-threading is implied; you are supposed to hack that
# yourself, or use a single instance per application. yourself, or use a single instance per application.
#
# Each instance is parametrized with two functions, one that is
# supposed to return the current time, one that is supposed to
# implement a delay. You can implement real-time scheduling by
# substituting time and sleep from built-in module time, or you can
# implement simulated time by writing your own functions. This can
# also be used to integrate scheduling with STDWIN events; the delay
# function is allowed to modify the queue. Time can be expressed as
# integers or floating point numbers, as long as it is consistent.
# Events are specified by tuples (time, priority, action, argument). Each instance is parametrized with two functions, one that is
# As in UNIX, lower priority numbers mean higher priority; in this supposed to return the current time, one that is supposed to
# way the queue can be maintained fully sorted. Execution of the implement a delay. You can implement real-time scheduling by
# event means calling the action function, passing it the argument. substituting time and sleep from built-in module time, or you can
# Remember that in Python, multiple function arguments can be packed implement simulated time by writing your own functions. This can
# in a tuple. The action function may be an instance method so it also be used to integrate scheduling with STDWIN events; the delay
# has another way to reference private data (besides global variables). function is allowed to modify the queue. Time can be expressed as
# Parameterless functions or methods cannot be used, however. 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
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
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 # XXX The timefunc and delayfunc should have been defined as methods
# XXX so you can define new kinds of schedulers using subclassing # XXX so you can define new kinds of schedulers using subclassing
# XXX instead of having to define a module or class just to hold # XXX instead of having to define a module or class just to hold
# XXX the global state of your particular time and delay functtions. # XXX the global state of your particular time and delay functions.
import bisect import bisect
class scheduler: class scheduler:
#
# Initialize a new instance, passing the time and delay functions
#
def __init__(self, timefunc, delayfunc): def __init__(self, timefunc, delayfunc):
"""Initialize a new instance, passing the time and delay
functions"""
self.queue = [] self.queue = []
self.timefunc = timefunc self.timefunc = timefunc
self.delayfunc = delayfunc self.delayfunc = delayfunc
#
# Enter a new event in the queue at an absolute time.
# Returns an ID for the event which can be used
# to remove it, if necessary.
#
def enterabs(self, time, priority, action, argument): def enterabs(self, time, priority, action, argument):
"""Enter a new event in the queue at an absolute time.
Returns an ID for the event which can be used to remove it,
if necessary.
"""
event = time, priority, action, argument event = time, priority, action, argument
bisect.insort(self.queue, event) bisect.insort(self.queue, event)
return event # The ID return event # The ID
#
# A variant that specifies the time as a relative time.
# This is actually the more commonly used interface.
#
def enter(self, delay, priority, action, argument): def enter(self, delay, priority, action, argument):
"""A variant that specifies the time as a relative time.
This is actually the more commonly used interface.
"""
time = self.timefunc() + delay time = self.timefunc() + delay
return self.enterabs(time, priority, action, argument) return self.enterabs(time, priority, action, argument)
#
# 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.
#
def cancel(self, event): def cancel(self, event):
"""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.
"""
self.queue.remove(event) self.queue.remove(event)
#
# Check whether the queue is empty.
#
def empty(self): def empty(self):
"""Check whether the queue is empty."""
return len(self.queue) == 0 return len(self.queue) == 0
#
# Run: execute events until the queue is empty.
#
# When there is a positive delay until the first event, the
# delay function is called and the event is left in the queue;
# otherwise, the event is removed from the queue and executed
# (its action function is called, passing it the argument).
# If the delay function returns prematurely, it is simply
# restarted.
#
# It is legal for both the delay function and the action
# function to to modify the queue or to raise an exception;
# 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:
# just after an event is executed, a delay of 0 is executed,
# to avoid monopolizing the CPU when other threads are also
# runnable.
#
def run(self): def run(self):
"""Execute events until the queue is empty.
When there is a positive delay until the first event, the
delay function is called and the event is left in the queue;
otherwise, the event is removed from the queue and executed
(its action function is called, passing it the argument). If
the delay function returns prematurely, it is simply
restarted.
It is legal for both the delay function and the action
function to to modify the queue or to raise an exception;
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:
just after an event is executed, a delay of 0 is executed, to
avoid monopolizing the CPU when other threads are also
runnable.
"""
q = self.queue q = self.queue
while q: while q:
time, priority, action, argument = q[0] time, priority, action, argument = q[0]
@ -96,4 +102,3 @@ class scheduler:
del q[0] del q[0]
void = apply(action, argument) void = apply(action, argument)
self.delayfunc(0) # Let other threads run self.delayfunc(0) # Let other threads run
#