The sched module defines a class which implements a general purpose event scheduler:
>>> 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
In multi-threaded environments, the scheduler class has limitations with respect to thread-safety, inability to insert a new task before the one currently pending in a running scheduler, and holding up the main thread until the event queue is empty. Instead, the preferred approach is to use the threading.Timer class instead.
>>> import time >>> from threading import Timer >>> def print_time(): ... print("From print_time", time.time()) ... >>> def print_some_times(): ... print(time.time()) ... Timer(5, print_time, ()).start() ... Timer(10, print_time, ()).start() ... time.sleep(11) # sleep while time-delay events execute ... print(time.time()) ... >>> print_some_times() 930343690.257 From print_time 930343695.274 From print_time 930343700.273 930343701.301
scheduler instances have the following methods and attributes:
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 cancel()).
Run all scheduled events. This function 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.
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.