if (__name__ == '__main__'): main(sys.argv[1:])

[Eli Stevens (WG.c)]

I have a question about proper Python style when it comes to having a main
function in a module.  I'm fairly new to Python - a few months of
very-part-time tinkering (lots'o'Java at work, shrug); my apologies if this
has been hashed out before.  Random Googling didn't enlighten me, so instead
I'll ask here.  :)

Take the following strmod.py (it's silly, I know):
----
import sys
import getopt

def main(sys_argv):
  try:
    opts, args = getopt.getopt(sys_argv, "clstu")

    for str_toPrint in args:
      for opt, arg in opts:
        if opt == '-c':
          str_toPrint = str_toPrint.capitalize()
        elif opt == '-l':
          str_toPrint = str_toPrint.lower()
        elif opt == '-s':
          str_toPrint = str_toPrint.swapcase()
        elif opt == '-t':
          str_toPrint = str_toPrint.title()
        elif opt == '-u':
          str_toPrint = str_toPrint.upper()

      print str_toPrint
  except getopt.GetoptError:
    pass


if (__name__ == '__main__'):
  main(sys.argv[1:])
----

Now, from what I have seen in terms of examples etc. would do something like
(note the lack of sys_argv, and how sys.argv[1:] is imbedded in the
getop.getopt call):

----
import sys
import getopt

def main():
  try:
    opts, args = getopt.getopt(sys.argv[1:], "clstu")
# ...
      print str_toPrint
  except getopt.GetoptError:
    pass


if (__name__ == '__main__'):
  main()
----

This essentially makes strmod.main() uncallable by anything else that needs
command line args, right?  The first pattern allows calls like
strmod.main("-t -s pRINT mE tHE sAME uNTESTED".split()) from elsewhere.  It
seems to me that this would be very helpful when writing low-level utilities
that could be driven by other higher-level utilities without needing to fall
back to OS calls, etc.

So...  Is this a good idea?  Bad idea?  Is there a better way?  I'm just
trying to not fall into any newbie pit traps ("Hey, what's at the bottom of
this nifty hole?" ;).

TIA,
Eli

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