Re: Is inifinite loop not a good practice?
Alvin A. Delagon enlightened us with: I have to write a python script that would continously monitor and process a queue database. [...] I've been planning to do an infinite loop within the script to do this but I've been hearing comments that infinite loop is a bad programming practice. I think it's just fine. You could improve it a bit by using something like: class Monitor(Thread): def __init__(self, *args, **kwargs): Thread.__init__(self, *args, **kwargs) self.interrupted = False def run(self): while not interrupted: monitor() def interrupt(self): self.interrupted = True I'm opted to run the script via crontab but I consider it as my last resort. The advantage there is a stability issue. If your program quits, you've got a problem. Using crontab, the program is started over and over again, so even if it crashes, it'll be restarted in time for the next monitor run. Cron has been around for such a long time that the chance of a crash is much less than with a freshly developed program. Sybren -- The problem with the world is stupidity. Not saying there should be a capital punishment for stupidity, but why don't we just take the safety labels off of everything and let the problem solve itself? Frank Zappa -- http://mail.python.org/mailman/listinfo/python-list
Re: Is inifinite loop not a good practice?
Thanks for the quick heads up! The comparison between implementing an infinite loop and cron is great. I'm beginning to see cron as the better solution between the two specially during crash instances. I'll try to code the script using the two solutions and do some stress testing to determine which is better between those two. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is inifinite loop not a good practice?
Alvin A. Delagon [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I've been hearing comments that infinite loop is a bad programming practice. What is bad is an *unintended* loop that goobles cpu time while outputting nothing. Example: def fact(n): res = 1 while n != 0: res *= n n -= 1 return res fact(-1) Now imagine that you are paying $360/hr ($.10/sec) (for IBM mainframe time) and you should understand the bad reputation (and why jobs were submitted with a time limit!). ;-) Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Is inifinite loop not a good practice?
In article [EMAIL PROTECTED], Terry Reedy [EMAIL PROTECTED] wrote: Alvin A. Delagon [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I've been hearing comments that infinite loop is a bad programming practice. What is bad is an *unintended* loop that goobles cpu time while outputting nothing. Example: def fact(n): res = 1 while n != 0: res *= n n -= 1 return res fact(-1) Now imagine that you are paying $360/hr ($.10/sec) (for IBM mainframe time) and you should understand the bad reputation (and why jobs were submitted with a time limit!). ;-) Terry Jan Reedy Could be worse. You could have written: def fact(n): if n == 0: return 1 else: return n * fact (n-1) then you would have not only gotten zonked on CPU charges, but on memory charges as well :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Is inifinite loop not a good practice?
Em Seg, 2006-02-20 às 17:01 -0500, Roy Smith escreveu: In article [EMAIL PROTECTED], Terry Reedy [EMAIL PROTECTED] wrote: def fact(n): res = 1 while n != 0: res *= n n -= 1 return res fact(-1) Could be worse. You could have written: def fact(n): if n == 0: return 1 else: return n * fact (n-1) then you would have not only gotten zonked on CPU charges, but on memory charges as well :-) This is not worse. Sometime in the future the function will raise a RuntimeError with maximum recursion depth exceeded and free all system resources, but the other one (without recursive calls) will only grow and grow and grow... -- Quem excele em empregar a força militar subjulga os exércitos dos outros povos sem travar batalha, toma cidades fortificadas dos outros povos sem as atacar e destrói os estados dos outros povos sem lutas prolongadas. Deve lutar sob o Céu com o propósito primordial da 'preservação'. Desse modo suas armas não se embotarão, e os ganhos poderão ser preservados. Essa é a estratégia para planejar ofensivas. -- Sun Tzu, em A arte da guerra -- http://mail.python.org/mailman/listinfo/python-list
Is inifinite loop not a good practice?
Greetings, I have to write a python script that would continously monitor and process a queue database. Once the script sees an unprocessed record it will create a thread to process it otherwise it will do nothing. I've been planning to do an infinite loop within the script to do this but I've been hearing comments that infinite loop is a bad programming practice. I'm opted to run the script via crontab but I consider it as my last resort. Do you have any suggestions on the design? Thanks in advance! -- http://mail.python.org/mailman/listinfo/python-list
Re: Is inifinite loop not a good practice?
Alvin A. Delagon wrote: Greetings, I have to write a python script that would continously monitor and process a queue database. Once the script sees an unprocessed record it will create a thread to process it otherwise it will do nothing. I've been planning to do an infinite loop within the script to do this but I've been hearing comments that infinite loop is a bad programming practice. I'm opted to run the script via crontab but I consider it as my last resort. Do you have any suggestions on the design? Thanks in advance! Clearly no process written as an infinite look is expected to run forever - it will be brought down by system reboots, for example, without going into end-of-life issues. The classic network server process is pretty much an infinite loop, though perhaps with a break condition actioned when the operator sets some flag with a command, and there's no real reason why you shouldn't cast your application as such a loop. You will need to do so with care, however. The danger is that you will spend time that should really be allocated to other processes on the system checking for database updates. So you need to design your polling mechanism fairly carefully - perhaps it could sleep five seconds once it found there were no more records that needed processing before looking again, or some similar mechanism to ensure that the system doesn't spend too much time looking for changes. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
