I've done some research and it seems that the sys.argv might require an argument at the command line when running the script
Not might, but definitely requires. That's the whole point of sys.argv, it contains the command line arguments. Like any python array, accesing non-existent element raises IndexError.
Although the code uses try/except to trap some errors, the offending statement occurs in the first line.
So the script needs a directory name, and you can test if there is one by looking at len(sys.argv) and comparing to 1+number_of_requirements. The argv always contains the script name plus any user supplied parameters, usually space delimited but the user can override the space-split through quoting. If the user does not supply the argument, your choices are supplying a default, prompting the user, or printing an exit error message.
To print an error and exit when the argument is missing, add this line before the first use of sys.argv:
if len(sys.argv)<2:
print "Fatal: You forgot to include the directory name on the command line."
print "Usage: python %s <directoryname>" % sys.argv[0]
sys.exit(1)
sys.argv[0] always contains the script name, and user inputs are placed in subsequent slots 1, 2, ...
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