[Tutor] Alarm Clock (suggestions please)

[ukapache]

John Fouhy wrote:
> 
> 2009/2/3 David <david at abbottdavid.com>:
>> while(doit):
>>        mytime = list(time.localtime())
>>        hour = mytime[3]
>>        minute = mytime[4]
>>        if hour == alarmhour and minute == alarmmin:
>>                subprocess.call('mplayer -loop 9 ring.wav', shell=True)
>>                sys.exit()
> 
> Hi David,
> 
> What you've written here is called a Busy Wait -- essentially, your
> program will be checking the local time as fast as it possibly can,
> which could be hundreds or thousands of times per second.  It will
> cause your CPU (or, at least, the core python is on) to run at 100%.
> 
> I imagine you don't actually care if your alarm is a few milliseconds
> late, so you could add a call to time.sleep(1) to the body of the
> loop. This will cause python to sleep for one second every iteration,
> thus allowing other programs to get some CPU time, and saving your
> power bill.
> 
> (in fact, since you're only specifying hour and minute for your alarm,
> you may as well sleep for 60 seconds each iteration)
> 
> Also, you could just write while(True).  Your control variable doit
> isn't actually doing anything in this program.
> 
> Regarding error checking, you could do tests to make sure the hour and
> minutes are in-range.  Perhaps you could add code to check whether the
> alarm time is more than a certain number of hours in the future.
> Depends how complex you want to make it.
> 
> (you could also inspect sys.argv -- this would allow you to specify
> the time on the command line, rather than requiring user input)
> 
> -- 
> John.
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
> 
> 


Hi

This is my first post so please be gentle, have been teaching myself python
for the last two months....

If you know the current local time  (time.localtime()) and the time you want
to wake up.... why not when you submit the program work out the difference
and make the alarm sleep for that time interval? 

Simon
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