I highly recommend argparse which comes with Python 2.7 and later.

The argparse module reduces boiler plate code and makes your code more robust, because the module handles all standard use cases (including subcommands), generates the help and usage for you, checks and sanitize the user input - all stuff you have to worry about when you are using sys.argv approach. And it is for free (built-in).

Here a small example:

import argparse

parser = argparse.ArgumentParser("simple_example")
parser.add_argument("counter", help="An integer will be increased by 1 and printed.", type=int)
args = parser.parse_args()
print(args.counter + 1)

and the output for python prog.py -h

usage: simple_example [-h] counter
    
positional arguments:
  counter     counter will be increased by 1 and printed.
    
optional arguments:
  -h, --help  show this help message and exit

and the output for python prog.py 1 As one would expect:

2

You can use the argv from sys

from sys import argv
arg1, arg2, arg3, ... = argv

You can actually put an abitrary number of arguments in the command line. argv will be a list with the arguments. Thus it can also be called as arg1 = sys.argv[0] arg2 = sys.argv[1] . . .

Keep also in mind that sys.argv[0] is simply the name of your python program. Additionally, the "eval" and "exec" functions are nice when you use command line input. Usually, everything in the command line is interpreted as a string. So, if you want to give a formula in the command line you use eval().

>>> x = 1
>>> print eval('x+1')
2