groking command line parameters in a python script

Question

I am relatively new to python. I want to write a script and pass it parameters like this:

myscript.py --arg1=hello --arg2=world

In the script, I want to access the arguments arg1 and arg2. Can anyone explains how to access command line parameters in this way?

Answer 1

Argparse is part of the standard library (as of versions 2.7 and 3.2). This is the module I use to handle all my command line parsing although there is also optparse (which is now deprecated) and getopt.

The following is a simple example of how to use argparse:

import sys, argparse

def main(argv=None):

    if argv is None:
        argv=sys.argv[1:]

    p = argparse.ArgumentParser(description="Example of using argparse")

    p.add_argument('--arg1', action='store', default='hello', help="first word")
    p.add_argument('--arg2', action='store', default='world', help="second word")

    # Parse command line arguments
    args = p.parse_args(argv)

    print args.arg1, args.arg2

    return 0

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

Edit: Note that the use of the leading '--' in the calls to add_arguments make arg1 and arg2 optional arguments, so I have supplied default values. If you want to program to require two arguments, remove these two leading hypens and they will become required arguments and you won't need the default=... option. (Strictly speaking, you also don't need the action='store' option, since store is the default action).