Application-global "switches"?

[Ethan Furman]

ici wrote:
> On Sep 4, 9:29 pm, kj <no.em... at please.post> wrote:
> 
>>I'm looking for the "best-practice" way to define application-global
>>read-only switches, settable from the command line.  The best
>>example I can think of of such global switch is the built-in variable
>>__debug__.  This variable is visible everywhere in a program, and
>>broadly affects its operation.
>>
>>The situation that prompts this question is the task of implementing
>>a certain application that is supposed to run for several days
>>(typically 2-3 weeks).  It is important to be able to re-start this
>>application where it left off in case that, for some reason (e.g.
>>internet connection failure), it terminates prematurely.  When this
>>application is restarted its behavior is somewhat different from
>>when it is started from scratch.  (For example, when it is re-started,
>>it does not clear certain directories.)
>>
>>Hence, I'd like to be able to have a variable, e.g. CONTINUATION_MODE,
>>visible everywhere in the code, that tells the application to behave
>>in "continuation mode", so that I can write stuff like
>>
>>    if not CONTINUATION_MODE:
>>        clean_the_slate()
>>
>>The only solution I can come up with is to define a "dummy module",
>>say _config.py, which contains only upper-case variables representing
>>these global switches, and is imported by all the other modules in
>>the application with the line "from _config import *".  During the
>>early stages of the run, the script inspects the command-line flags,
>>and if it finds a --continuing flag, it sets the variable
>>_config.CONTINUATION_MODE to True.  (The last point implies that
>>these variables are not strictly speaking read-only, since they
>>most be set at the beginning of the run.  But after this initial
>>setting, they should remain read-only.)
>>
>>I'm sure this would work OK, but I wonder if there is a more Pythonic
>>way to do this sort of thing.  Is there a best practice for setting
>>such application-global switches?
>>
>>TIA!
>>
>>kynn
> 
> 
> while 1:
>   try:
>     run_main_code()
>     cleanup()
>   except:
>     while conn_fail():
>        time.sleep(5.0)
>   finally:
>     cleanup_all()

How will this restart the OP's process with all files still in place and 
continuation mode on?

~Ethan