sched
— 事件调度器
¶
源代码： Lib/sched.py
sched
module defines a class which implements a general purpose event scheduler:
sched.
scheduler
(
timefunc=time.monotonic
,
delayfunc=time.sleep
)
¶
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). If time.monotonic is not available, the
timefunc
default is time.time instead. 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.
3.3 版改变： timefunc and delayfunc parameters are optional.
3.3 版改变：
scheduler
class can be safely used in multi-threaded environments.
范例：
>>> import sched, time
>>> s = sched.scheduler(time.time, time.sleep)
>>> def print_time(a='default'):
... print("From print_time", time.time(), a)
...
>>> def print_some_times():
... print(time.time())
... s.enter(10, 1, print_time)
... s.enter(5, 2, print_time, argument=('positional',))
... s.enter(5, 1, print_time, kwargs={'a': 'keyword'})
... s.run()
... print(time.time())
...
>>> print_some_times()
930343690.257
From print_time 930343695.274 positional
From print_time 930343695.275 keyword
From print_time 930343700.273 default
930343700.276
scheduler
instances have the following methods and attributes:
scheduler.
enterabs
(
time
,
priority
,
action
,
argument=()
,
kwargs={}
)
¶
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 . A lower number represents a higher priority.
Executing the event means executing
action(*argument,
**kwargs)
.
argument
is a sequence holding the positional arguments for
action
.
kwargs
is a dictionary holding the keyword arguments for
action
.
Return value is an event which may be used for later cancellation of the event (see
cancel()
).
3.3 版改变： argument parameter is optional.
3.3 版新增： kwargs 参数被添加。
scheduler.
enter
(
delay
,
priority
,
action
,
argument=()
,
kwargs={}
)
¶
Schedule an event for
delay
more time units. Other than the relative time, the other arguments, the effect and the return value are the same as those for
enterabs()
.
3.3 版改变： argument parameter is optional.
3.3 版新增： kwargs 参数被添加。
scheduler.
cancel
(
event
)
¶
Remove the event from the queue. If
event
is not an event currently in the queue, this method will raise a
ValueError
.
scheduler.
empty
(
)
¶
Return true if the event queue is empty.
scheduler.
run
(
blocking=True
)
¶
Run all scheduled events. This method will wait (using the
delayfunc()
function passed to the constructor) for the next event, then execute it and so on until there are no more scheduled events.
若 blocking is false executes the scheduled events due to expire soonest (if any) and then return the deadline of the next scheduled call in the scheduler (if any).
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
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.
3.3 版新增： blocking 参数被添加。