The rap against "while True:" loops
jack at 0x6a.com
Wed Oct 14 20:51:11 CEST 2009
> I'm coaching a group of biologists on basic Python scripting. One
> of my charges mentioned that he had come across the advice never
> to use loops beginning with "while True". Of course, that's one
> way to start an infinite loop, but this seems hardly a sufficient
> reason to avoid the construct altogether, as long as one includes
> an exit that is always reached. (Actually, come to think of it,
> there are many situations in which a bona fide infinite loops
> (typically within a try: block) is the required construct, e.g.
> when implementing an event loop.)
> I use "while True"-loops often, and intend to continue doing this
> "while True", but I'm curious to know: how widespread is the
> injunction against such loops? Has it reached the status of "best
This thread has gotten a lot of posts concerning programming practices
and dogma alike. I'd like to add a personal use of `while True:` that
has nothing to do with either best practices or dogma.
I use python a *lot* to do day-to-day tasks in an engineering lab. I
use it to control, log, or otherwise converse with rs232 based gear, as
well as use it to back up or organize documents, etc... (lo and behold,
I use this scripting language to write little scripts here and there).
Don't get me wrong, I also write full blown control/logging apps with
python, but that is only 10% of my usage.
Whenever I need to quickly log something (serial output of a device)
quickly, I find myself writing this in the python REPL:
comport = serial.Serial('COMx', timeout=1)
get = comport.readline()
It is short enough that I don't see the need to write my own module.
Sometimes I even add a little regexp based filtering -- which adds 2
lines total. When I am done logging I just give 'er a CTRL-C and be
done with it. It is also a hell of a lot less buggy and error prone
than hyperterminal, which my boss uses to do the same thing.
I think this is a perfect example of `while True:` that works damn well,
and there isn't anything that can replace its simplicity. Programming
practices be damned, it is invaluable, and I would recommend doing it in
my situation to any person, regardless of programming experience.
Food for thought.
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