How to read/process command line arguments?

Question

import sys

print("\n".join(sys.argv))

sys.argv is a list that contains all the arguments passed to the script on the command line. sys.argv[0] is the script name.

Basically,

import sys
print(sys.argv[1:])

The canonical solution in the standard library is argparse (docs):

Here is an example:

from argparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument("-f", "--file", dest="filename",
                    help="write report to FILE", metavar="FILE")
parser.add_argument("-q", "--quiet",
                    action="store_false", dest="verbose", default=True,
                    help="don't print status messages to stdout")

args = parser.parse_args()

argparse supports (among other things):

• Multiple options in any order.
• Short and long options.
• Default values.
• Generation of a usage help message.

Just going around evangelizing for argparse which is better for these reasons.. essentially:

(copied from the link)

• argparse module can handle positional and optional arguments, while optparse can handle only optional arguments

• argparse isn’t dogmatic about what your command line interface should look like - options like -file or /file are supported, as are required options. Optparse refuses to support these features, preferring purity over practicality

• argparse produces more informative usage messages, including command-line usage determined from your arguments, and help messages for both positional and optional arguments. The optparse module requires you to write your own usage string, and has no way to display help for positional arguments.

• argparse supports action that consume a variable number of command-line args, while optparse requires that the exact number of arguments (e.g. 1, 2, or 3) be known in advance

• argparse supports parsers that dispatch to sub-commands, while optparse requires setting allow_interspersed_args and doing the parser dispatch manually

And my personal favorite:

• argparse allows the type and action parameters to add_argument() to be specified with simple callables, while optparse requires hacking class attributes like STORE_ACTIONS or CHECK_METHODS to get proper argument checking

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

If you need something fast and not very flexible

main.py:

import sys

first_name = sys.argv[1]
last_name = sys.argv[2]
print("Hello " + first_name + " " + last_name)

Then run python main.py James Smith

to produce the following output:

Hello James Smith

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

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)