Optparser-print Usage Help when no argument is given

Question

What I am doing now is to simply check for args length, if it is 0, tell user to type -h.

Is there a better way to do this ? Thanks

Answer 1

You can do it with optparse just fine. You don't need to use argparse.

if options.foo is None: # where foo is obviously your required option
    parser.print_help()
    sys.exit(1)

Answer 2

It's not clear from your question whether you are using the (deprecated) optparse module or its replacement, the argparse module. Assuming the latter, then as long as you have at least one positional argument your script will print out a usage message if no arguments (or insufficient arguments) are supplied.

Here's an example script:

import argparse

parser = argparse.ArgumentParser(description="A dummy program")
parser.add_argument('positional', nargs="+", help="A positional argument")
parser.add_argument('--optional', help="An optional argument")

args = parser.parse_args()

If I run this with no arguments, I get this result:

usage: script.py [-h] [--optional OPTIONAL] positional [positional ...]
script.py: error: too few arguments