flag.py

#!/usr/bin/env python3
import argparse
import string
import sys

CHARS = ("🇦", "🇧", "🇨", "🇩", "🇪", "🇫", "🇬", "🇭", "🇮", "🇯", "🇰", "🇱", "🇲",
         "🇳", "🇴", "🇵", "🇶", "🇷", "🇸", "🇹", "🇺", "🇻", "🇼", "🇽", "🇾", "🇿")

OFFSET = ord('A')

def flag(code):
    """
    Return the Unicode flag emoji for a two-letter country code.

    """
    if len(code) != 2:
        raise ValueError('country code must be two letters long')
    if not all(c in string.ascii_letters for c in code):
        raise ValueError('country code must only contain letters A-Z')

    return ''.join(CHARS[ord(c) - OFFSET] for c in code.upper())

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('country_code', nargs='*',
                        help='a two-letter country code (ISO 3166-1)')
    parser.add_argument('-s', '--sep', help='separator')
    args = parser.parse_args()

    if args.country_code:
        flags = (flag(code) for code in args.country_code)
    else:
        parser.print_help()
        return 1

    sep = ' ' if args.sep is None else args.sep
    print(sep.join(flags))

if __name__ == '__main__':
    sys.exit(main())