Command Line Arguments in Python

What is command line arguments in Python?

Python supports the creation of programs that can be run on the command line, complete with command-line arguments. It provides a getopt module, with which command-line options and arguments can be parsed.

Accessing Command Line Arguments

The Python sys module provides access to any of the command-line arguments via sys.argv. It solves two purposes:

• sys.argv is the list of command-line arguments
• len(sys.argv) is the number of command-line arguments that you have in your command line
• sys.argv[0] is the program, i.e. script name

Executing Python

You can execute Python in this way:

$python Commands.py inp1, inp2 inp3

How do you pass an argument in Python?

In Python, if a script is invoked from a shell, the arguments will be placed after the name of the script. Here the arguments will be separated by spaces and within the script those arguments will be accessible via list variable sys. argv.

Example

Inside Commands.py:

import sys

print ‘Number of arguments:’, len (sys.argv), ‘arguments.’

print ‘Argument List:’, str(sys.argv)

It will produce the following output:

Number of arguments: 4 arguments.

Argument List: [‘sample.py’, ‘inp1’, ‘inp2’, ‘inp3’]

Note: One thing to remember here is that indentation and spacing is extremely important, otherwise it may give error or incorrect number of arguments.

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