On Aug 22, 1:30 pm, Karthik Gurusamy <[EMAIL PROTECTED]> wrote: > Hi, > > I'm working on a cron like functionality for my application. > The outer loops runs continuously waking every x seconds (say x=180, > 300, ..). > It needs to know what events in cron has expired and for each event do > the work needed. > > It's basically like unix cron or like a calendar application with some > restrictions. The outer loop may come back a lot later and many events > might have missed their schedule -- but this is okay.. We don't have > to worry about missed events (if there were n misses, we just need to > execute call back once). > > Let's take some examples [Let e denotes an event] > e1: hour=1 min=30 # Run every day once at > 1:30 AM > e2: wday=0, hour=1 min=0 # run every Monday at 1 AM > e3: month=10, day=10, hour=10 min=0 # run on October 10th, 10 AM > every year > > class Cron_Event (object): > def __init__ (year=None, month=None, day=None, hour=None ..etc) > # do init > > class Cron (object): > def __init__ (): > # do init > def event_add (e): > # add an event > def execute() > # see if any events has "expired" .. call it's callback > # I'm looking for ideas on how to manage the events here > > From outer loop > cron = Cron() > # create various events like > e1 = Cron_Event(hour=1) > cron.event_add(e1) > e2 = Cron_Event(wday=0, hour=1) > cron.event_add(e2) > > while True: > sleep x seconds (or wait until woken up) > cron.execute() > # do other work.. x may change here > > If I can restrict to hour and minute, it seems manageable as the > interval between two occurrences is a constant. But allowing days like > every Monday or 1st of every month makes things complicated. Moreover > I would like each constraint in e to take on multiple possibilities > (like every day at 1AM, 2 AM and 4 AM do this). > > I'm looking for solutions that can leverage datetime.datetime > routines. > My current ideas include for each e, track the next time it will fire > (in seconds since epoch as given by time.time()). Once current time > has passed that time, we execute the event. e.g.>>> datetime.datetime.now() > > datetime.datetime(2008, 8, 22, 13, 19, 54, 5567)>>> time.time() > > 1219436401.741966 <--- compute event's next firing in a format like > this > > > > The problem seems to be how to compute that future point in time (in > seconds since epoch) for a generic Cron_Event. > > Say how do I know the exact time in future that will satisfy a > constraint like: > month=11, wday=1, hour=3, min=30 # At 3:30 AM on a Tuesday in > November > > Thanks for your thoughts. > > Karthik
I only scanned your message, but maybe datetime.timedelta() will help.. >>> import datetime >>> now = datetime.datetime.now() >>> print now 2008-08-22 13:48:49.335225 >>> day = datetime.timedelta(1) >>> print day 1 day, 0:00:00 >>> print now + day 2008-08-23 13:48:49.335225 ~Sean -- http://mail.python.org/mailman/listinfo/python-list
