Script to rename all files in current directory

ISODateRename.py

import os, re, argparse, sys
from datetime import datetime

parser = argparse.ArgumentParser(description='Rename files to have a prefix of their created date.')
parser.add_argument('-v', '--version', action='version', version='%(prog)s v2.0', help='Display the version of the program.')
parser.add_argument('-f', '--file', default=' ', type=str, help='Choose which file to rename.')
parser.add_argument('-d', '--directory', default='./', type=str, help='Choose a directory to rename all files in.')
parser.add_argument('-i', '--ignore', default='@', type=str, help='Choose ignore files starting with a character.')
args = parser.parse_args()

rename_dir = args.directory
ignore_char = args.ignore

if not rename_dir.endswith('/'):
    rename_dir += '/'

def yes(confirm):
    return (confirm == '') or (re.match('^y(es)?$', confirm) is not None)

def no(confirm):
    return re.match('^no?$', confirm) is not None

def confirm_loop(msg):
    sys.stdout.write(msg)
    confirm = input().lower()

    if yes(confirm):
        return True
    elif no(confirm):
        return False
    else:
        print('Invalid response\n')
        return confirm_loop()

def rename_files():
    amt = 0
    files = [f for f in next(os.walk(rename_dir))[2] if not f.startswith(ignore_char)]

    if len(files) == 0:
        return 0
    else:
        for file in files:
            rename_file(rename_dir + file)
            amt += 1

    return amt

def rename_file(file):
    file_time = datetime.fromtimestamp(os.stat(file).st_mtime)
    file_name = '{}{}-{}-{} {}'.format(rename_dir, str(file_time.year), str(file_time.month).zfill(2), str(file_time.day).zfill(2), file[len(rename_dir):])
    
    os.rename(file, file_name)
    print('Renamed "{}"'.format(file_name[len(rename_dir):]))

if args.file == ' ':
    print('This will rename all files in "{}" except those starting with "{}".'.format(rename_dir, ignore_char))
    
    if confirm_loop('Do you wish to continue [Y/n]? '):
        rename_amt = rename_files()
        print('Renamed {} files.'.format(rename_amt))
    else:
        print('Exiting...')
        sys.exit()
else:
    print('This will rename the file "{}"'.format(args.file))

    if (confirm_loop('Do you wish to continue [Y/n]? ')):
        rename_file(args.file)
    else:
        print('Exiting...')
        sys.exit()