python function as script

README.md

Python Function as Script

This is a quick demonstration of how to create a function that can be used as either:

• command-line script with parameters, or
• imported module function

Running in Command-Line

Direct

$ python mod.py abc --list xyz,123
x = 'abc'
y = ['xyz', '123']

Run Module

Alternatively, it can be run as a module. This will search the sys.path for a module with the same name and run it like the script above.

$ python -m mod abc --list xyz,123
x = 'abc'
y = ['xyz', '123']

Help Output

$ python mod.py --help
usage: mod.py [-h] [--list LIST] [x]

Do some stuff

positional arguments:
  x                     A value with some meaning

optional arguments:
  -h, --help            show this help message and exit
  --list LIST, -l LIST  CSV list of things

Importing function

>>> from mod import foo
>>> foo('abc', ['xyz', '123'])
x = 'abc'
y = ['xyz', '123']

mod.py

#!/usr/bin/env python

def foo(x, y):
    print('x = {!r}'.format(x))
    print('y = {!r}'.format(y))


if __name__ == '__main__':
    import argparse
    
    # Parse command-line parameters
    parser = argparse.ArgumentParser(description="Do some stuff")

    def csv_list(value):
        return value.split(',')
    
    parser.add_argument(
        'x', nargs='?', default='blah',
        help="A value with some meaning",
    )
    parser.add_argument(
        '--list', '-l', dest='list',
        type=csv_list, default=[],
        help="CSV list of things",
    )

    args = parser.parse_args()

    # Run method with command-line arguments
    foo(x=args.x, y=args.list)