Parsing arguments

When writing command-line tools, it's usually common to have it change behavior based on options provided to the executable. These options are usually available in sys.argv together with the executable name, but parsing them is not as easy as it might seem, especially when multiple arguments must be supported. Also, when an option is malformed, it's usually a good idea to provide a usage message to inform the user about the right way to use the tool.

How to do it...

Perform the following steps for this recipe:

1. The argparse.ArgumentParser object is the primary object in charge of parsing command-line options:

import argparse
import operator
import logging
import functools

parser = argparse.ArgumentParser(
    description='Applies an operation to one or more numbers'
)
parser.add_argument("number", 
                    help="One or more numbers to perform an operation on.",
                    nargs='+', type=int)
parser.add_argument('-o', '--operation', 
                  ...