Argparse Example with Date and Directory Validation

sample.py

import argparse
import arrow
import pathlib

def valid_date_arg(value):
    """ Used by argparser to validate date arguments """
    try:
        return arrow.get(value, 'YYYY-MM-DD')
    except arrow.parser.ParserError:
        msg = f'Not a valid date in YYYY-MM-DD format: "{value}"'
        raise argparse.ArgumentTypeError(msg)

        
def valid_filepath_arg(value):
    """ Used by argparse to see if a file exists """
    filepath = pathlib.Path(value)

    if not filepath.exists():
        msg = f'File "{arg}" does not exist'
        raise argparse.ArgumentTypeError(msg)
    else:
        return filepath
        
        
def valid_dir_arg(value):
    """ Used by argparse to see if a directory exists """
    filepath = pathlib.Path(value)
    
    if not filepath.exists() or not filepath.is_dir():
        msg = f'Directory "{arg}" does not exist'
        raise argparse.ArgumentTypeError(msg)
    else:
        return filepath        
        
        
# Read command-line arguments
argparser = argparse.ArgumentParser()
argparser.add_argument('date', type=valid_date_arg)
argparser.add_argument('directory', type=valid_dir_arg)
args = argparser.parse_args()