Python Argparse Example

argparse_example.py

import argparse
import pathlib

def valid_dir_arg(value):
    """ Used by argparse to determine if the value is a valid directory """
    filepath = pathlib.Path(value)

    if not filepath.exists() or not filepath.is_dir():
        msg = f'Error! This is not a directory: {value}'
        raise argparse.ArgumentTypeError(msg)
    else:
        return filepath
    

def valid_filepath_arg(value):
    filepath = pathlib.Path(value)

    if not filepath.exists():
        msg = f'File  not found: {value}'
        raise argparse.ArgumentTypeError(msg)
    else:
        return filepath


def valid_date_arg(value):
    try:
        date = arrow.get(value, 'YYYY-MM-DD')
        return date
    except arrow.parser.ParserError:
        msg = 'Invalid date. Must be YYYY-MM-DD format.'
        raise argparse.ArgumentTypeError(msg)


if __name__ == '__main__':

    # Read command-line arguments
    argparser = argparse.ArgumentParser()
    argparser.add_argument('src_filepath', type=valid_filepath_arg)
    argparser.add_argument('date', type=valid_date_arg)
    args = argparser.parse_args()
    
    print(args.src_filepath)
    print(args.date)