CLI Program Arguments

Table of contents

1. Description
2. argv.py
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3. addition-cli.py
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Description

Programs can be written to accept command-line arguments when they are executed. This requires the use of the sys.argv list.

• The first item in this list (index 0) is always the name of the file being executed.
• Any additional items in this list are arguments supplied on the command line.
• The module sys must be imported to access the sys.argv list.

argv.py

The following program prints items in the sys.argv list. It is saved in the /Users/bianca/test directory.

import sys

def main():
    # print entire argv list:
    print(f'\nargv list: {sys.argv}')
    
    # print filename stored in first element:
    print(f'Filename:  {sys.argv[0]}')
    
    # print any command-line arguments:
    for argument in sys.argv[1:]:
        print(argument)
    
if __name__ == '__main__':
    main()

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addition-cli.py

The following program accepts two integer arguments from the command line, then displays the sum. It is saved in the /Users/bianca/test directory.

import sys

def main():
    try:
        number1 = int(sys.argv[1])
        number2 = int(sys.argv[2])
    except ValueError:
        print('\nYou must enter two integer arguments. Ending Execution')
        return
    
    print(f'\nThe sum is {number1 + number2}')

if __name__ == '__main__':
    main()

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