How do I access command line arguments?

Question

I use python to create my project settings setup, but I need help getting the command line arguments.

I tried this on the terminal:

$python myfile.py var1 var2 var3

In my Python file, I want to use all variables that are input.

Answer 1

Python tutorial explains it:

import sys

print(sys.argv)

More specifically, if you run python example.py one two three:

>>> import sys
>>> print(sys.argv)
['example.py', 'one', 'two', 'three']

Answer 2

To get only the command line arguments

(not including the name of the Python file)

import sys

sys.argv[1:]

The [1:] is a slice starting from the second element (index 1) and going to the end of the arguments list. This is because the first element is the name of the Python file, and we want to remove that.

Answer 3

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