How to read/process command line arguments?

Question

I am originally a C programmer. I have seen numerous tricks and \"hacks\" to read many different arguments.

What are some of the ways Python programmers can do this

Answer 1

The docopt library is really slick. It builds an argument dict from the usage string for your app.

Eg from the docopt readme:

"""Naval Fate.

Usage:
  naval_fate.py ship new <name>...
  naval_fate.py ship <name> move <x> <y> [--speed=<kn>]
  naval_fate.py ship shoot <x> <y>
  naval_fate.py mine (set|remove) <x> <y> [--moored | --drifting]
  naval_fate.py (-h | --help)
  naval_fate.py --version

Options:
  -h --help     Show this screen.
  --version     Show version.
  --speed=<kn>  Speed in knots [default: 10].
  --moored      Moored (anchored) mine.
  --drifting    Drifting mine.

"""
from docopt import docopt


if __name__ == '__main__':
    arguments = docopt(__doc__, version='Naval Fate 2.0')
    print(arguments)

Answer 2

#set default args as -h , if no args:
if len(sys.argv) == 1: sys.argv[1:] = ["-h"]

Answer 3

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))

Assuming the Python code above is saved into a file called prog.py
$ python prog.py -h

Ref-link: https://docs.python.org/3.3/library/argparse.html

Answer 4

There is also argparse stdlib module (an "impovement" on stdlib's optparse module). Example from the introduction to argparse:

# script.py
import argparse

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument(
        'integers', metavar='int', type=int, choices=range(10),
         nargs='+', help='an integer in the range 0..9')
    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))

Usage:

$ script.py 1 2 3 4
4

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

Answer 5

One way to do it is using sys.argv. This will print the script name as the first argument and all the other parameters that you pass to it.

import sys

for arg in sys.argv:
    print arg

Answer 6

My solution is entrypoint2. Example:

from entrypoint2 import entrypoint
@entrypoint
def add(file, quiet=True): 
    ''' This function writes report.

    :param file: write report to FILE
    :param quiet: don't print status messages to stdout
    '''
    print file,quiet

help text:

usage: report.py [-h] [-q] [--debug] file

This function writes report.

positional arguments:
  file         write report to FILE

optional arguments:
  -h, --help   show this help message and exit
  -q, --quiet  don't print status messages to stdout
  --debug      set logging level to DEBUG