How to use getopt/OPTARG in Python? How to shift arguments if too many arguments (9) are given?

Question

How to use getopt/optarg in Python?

Answer 1

This is an example of how I do it, I usually use the same basic template:

import sys
import getopt

try:
    opts, args = getopt.getopt(sys.argv[1:], 'm:p:h', ['miner=', 'params=', 'help'])
except getopt.GetoptError:
    usage()
    sys.exit(2)

for opt, arg in opts:
    if opt in ('-h', '--help'):
        usage()
        sys.exit(2)
    elif opt in ('-m', '--miner'):
        miner_name = arg
    elif opt in ('-p', '--params'):
        params = arg
    else:
        usage()
        sys.exit(2)

I don't think there is any 9 parameter limit.

Answer 2

Have you tried reading the python docs for the module getopt (http://docs.python.org/library/getopt.html?highlight=getopt#module-getopt)? It provides a simple example of how the getopt is used. What do you mean by shift arguments? If you want to check that the user does not use more than 9 arguments, you can check the length of the sys.argv list, which contains all the options/arguments passed to the script. The first element is the name of the script which is invoked, so the length is always at least 1. You could do something like:

if len(sys.argv) > 10
    print('Too many arguments.')

Answer 3

A google search would have helped. Have a look at the getopt and argparse modules in the standard library:

import argparse

parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('integers', metavar='N', type=int, nargs='+',
                   help='an integer for the accumulator')
parser.add_argument('--sum', dest='accumulate', action='store_const',
                   const=sum, default=max,
                   help='sum the integers (default: find the max)')

args = parser.parse_args()
print args.accumulate(args.integers)

Then run it as expected:

$ prog.py -h
usage: prog.py [-h] [--sum] N [N ...]

Process some integers.

positional arguments:
 N           an integer for the accumulator

optional arguments:
 -h, --help  show this help message and exit
 --sum       sum the integers (default: find the max)

When run with the appropriate arguments, it prints either the sum or the max of the command-line integers:

$ prog.py 1 2 3 4
4

$ prog.py 1 2 3 4 --sum
10

This is straight from the standard library.