[Tutor] Use flag to exit?

[Richard D. Moores]

On Wed, Jun 23, 2010 at 22:31, Richard D. Moores <rdmoores at gmail.com> wrote:
> I've read (I can't remember where) that for every prime p there there
> are positive integers a and b such that p = a + b and such that
> 2**a*3**b is either 1 greater than or 1 less than another (much
> larger) prime. I don't know if this has been proven or not, but I've
> tested it on all primes 3 < p <= 5689. Here's my script that produces
> a big prime number from a small one (p > 3):
> <http://tutoree7.pastebin.com/s09YniXG>.
>
> My question is how to best exit when the big prime has been found. I
> used a flag (see the highlighted lines 34,40,44), but I seem to
> remember that, though they can work, flags are frowned upon by
> Pythonistas, and should be used only when absolutely necessary. So, is
> one necessary in my script?
>
> Thanks,
>
> Dick Moores

Can't I use sys.exit(). In <http://tutoree7.pastebin.com/hU9DbMwH>.
For n = 333 I get the output

The prime greater than or equal to 333 is 337
The smaller prime 337 determined this much larger prime, which has 121 digits:
12965282936790350290684656658525333839833593063568777527873447337564535715481689470015706033552806
62151567471574769467391
a and b were 231 106
Traceback (most recent call last):
  File "C:/P31Working/prime_to_biggest_prime_tutor3.py", line 45, in <module>
    sys.exit()
SystemExit

How can I prevent

Traceback (most recent call last):
  File "C:/P31Working/prime_to_biggest_prime_tutor3.py", line 45, in <module>
    sys.exit()
SystemExit

from printing? Or isn't using sys.exit() a good idea?

Dick