[Tutor] IOError exception handling

[Sean 'Shaleh' Perry]

> 
> Which works when I force errors of several types.  Do I need the
> sys.exit(1), and is 1 a reasonable generic number?  I've seen it in
> several examples, and since I'm still partly in monkey-see, monkey-do
> mode, I stuck it in even though it superficially works without it. :-)

without the sys.exit you would not exit (-: if you "need" it is another matter
and up to you.

As to the parameter for sys.exit(), 0 is success and non 0 is failure.  I often
use -1 for input issues and 1 for faults.

i.e.

if len(sys.argv) != 2:
  print 'Usage: app input'
  sys.exit(-1)

if not file_exists:
  sys.exit(1)