Checking if sys.argv[x] is defined

Question

What would be the best way to check if a variable was passed along for the script:

try:
    sys.argv[1]
except NameError:
    startingpoint = 'blah'
else:
    startingpoint = sys.argv[1]

Answer 1

Check the length of sys.argv:

if len(sys.argv) > 1:
    blah = sys.argv[1]
else:
    blah = 'blah'

Some people prefer the exception-based approach you've suggested (eg, try: blah = sys.argv[1]; except IndexError: blah = 'blah'), but I don't like it as much because it doesn't “scale” nearly as nicely (eg, when you want to accept two or three arguments) and it can potentially hide errors (eg, if you used blah = foo(sys.argv[1]), but foo(...) raised an IndexError, that IndexError would be ignored).