1
:mod:`sched` --- Event scheduler
2
================================
5
:synopsis: General purpose event scheduler.
7
.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
9
**Source code:** :source:`Lib/sched.py`
11
.. index:: single: event scheduling
15
The :mod:`sched` module defines a class which implements a general purpose event
18
.. class:: scheduler(timefunc=time.monotonic, delayfunc=time.sleep)
20
The :class:`scheduler` class defines a generic interface to scheduling events.
21
It needs two functions to actually deal with the "outside world" --- *timefunc*
22
should be callable without arguments, and return a number (the "time", in any
23
units whatsoever). If time.monotonic is not available, the *timefunc* default
24
is time.time instead. The *delayfunc* function should be callable with one
25
argument, compatible with the output of *timefunc*, and should delay that many
26
time units. *delayfunc* will also be called with the argument ``0`` after each
27
event is run to allow other threads an opportunity to run in multi-threaded
30
.. versionchanged:: 3.3
31
*timefunc* and *delayfunc* parameters are optional.
33
.. versionchanged:: 3.3
34
:class:`scheduler` class can be safely used in multi-threaded
39
>>> import sched, time
40
>>> s = sched.scheduler(time.time, time.sleep)
41
>>> def print_time(a='default'):
42
... print("From print_time", time.time(), a)
44
>>> def print_some_times():
45
... print(time.time())
46
... s.enter(10, 1, print_time)
47
... s.enter(5, 2, print_time, argument=('positional',))
48
... s.enter(5, 1, print_time, kwargs={'a': 'keyword'})
50
... print(time.time())
52
>>> print_some_times()
54
From print_time 930343695.274 positional
55
From print_time 930343695.275 keyword
56
From print_time 930343700.273 default
59
.. _scheduler-objects:
64
:class:`scheduler` instances have the following methods and attributes:
67
.. method:: scheduler.enterabs(time, priority, action, argument=(), kwargs={})
69
Schedule a new event. The *time* argument should be a numeric type compatible
70
with the return value of the *timefunc* function passed to the constructor.
71
Events scheduled for the same *time* will be executed in the order of their
74
Executing the event means executing ``action(*argument, **kwargs)``.
75
*argument* is a sequence holding the positional arguments for *action*.
76
*kwargs* is a dictionary holding the keyword arguments for *action*.
78
Return value is an event which may be used for later cancellation of the event
81
.. versionchanged:: 3.3
82
*argument* parameter is optional.
85
*kwargs* parameter was added.
88
.. method:: scheduler.enter(delay, priority, action, argument=(), kwargs={})
90
Schedule an event for *delay* more time units. Other than the relative time, the
91
other arguments, the effect and the return value are the same as those for
94
.. versionchanged:: 3.3
95
*argument* parameter is optional.
98
*kwargs* parameter was added.
100
.. method:: scheduler.cancel(event)
102
Remove the event from the queue. If *event* is not an event currently in the
103
queue, this method will raise a :exc:`ValueError`.
106
.. method:: scheduler.empty()
108
Return true if the event queue is empty.
111
.. method:: scheduler.run(blocking=True)
113
Run all scheduled events. This method will wait (using the :func:`delayfunc`
114
function passed to the constructor) for the next event, then execute it and so
115
on until there are no more scheduled events.
117
If *blocking* is false executes the scheduled events due to expire soonest
118
(if any) and then return the deadline of the next scheduled call in the
121
Either *action* or *delayfunc* can raise an exception. In either case, the
122
scheduler will maintain a consistent state and propagate the exception. If an
123
exception is raised by *action*, the event will not be attempted in future calls
126
If a sequence of events takes longer to run than the time available before the
127
next event, the scheduler will simply fall behind. No events will be dropped;
128
the calling code is responsible for canceling events which are no longer
131
.. versionadded:: 3.3
132
*blocking* parameter was added.
134
.. attribute:: scheduler.queue
136
Read-only attribute returning a list of upcoming events in the order they
137
will be run. Each event is shown as a :term:`named tuple` with the
138
following fields: time, priority, action, argument, kwargs.