#! /usr/bin/env python3
"""n2w: number to words conversion module: contains function
   num2words. Can also be run as a script
usage as a script: n2w num
           (Convert a number to its English word description)
           num: whole integer from 0 and 999,999,999,999,999 (commas are
           optional)
example: n2w 10,003,103
           for 10,003,103 say: ten million three thousand one hundred three
"""
import sys, string, argparse
_1to9dict = {'0': '', '1': 'one', '2': 'two', '3': 'three', '4': 'four',  #B
             '5': 'five', '6': 'six', '7': 'seven', '8': 'eight',
             '9': 'nine'}
_10to19dict = {'0': 'ten', '1': 'eleven', '2': 'twelve',
               '3': 'thirteen', '4': 'fourteen', '5': 'fifteen',
               '6': 'sixteen', '7': 'seventeen', '8': 'eighteen', 
               '9': 'nineteen'}
_20to90dict = {'2': 'twenty', '3': 'thirty', '4': 'forty', '5': 'fifty',
               '6': 'sixty', '7': 'seventy', '8': 'eighty', '9': 'ninety'}
_magnitude_list = [(0, ''), (3, ' thousand '), (6, ' million '), 
                  (9, ' billion '), (12, ' trillion '),(15, '')]
def num2words(num_string):
    """num2words(num_string): convert number to English words"""
    if num_string == '0':                                             #C
        return 'zero'
    num_string = num_string.replace(",", "")
    num_length = len(num_string) 
    max_digits = _magnitude_list[-1][0]
    if num_length > max_digits:
        return "Sorry, can't handle numbers with more than  " \
               "{0} digits".format(max_digits)
    num_string = '00' + num_string                                #D  #F
    word_string = ''   
                                           #E  #F
    for mag, name in _magnitude_list:                                 #F
        if mag >= num_length:                                         #F
            return word_string                                        #F
        else:                                                         #F
            hundreds, tens, ones = num_string[-mag-3], \
                 num_string[-mag-2], num_string[-mag-1]               #F
            if not (hundreds == tens == ones == '0'):                 #F
                word_string = _handle1to999(hundreds, tens, ones) + \
                                            name + word_string        #F
def _handle1to999(hundreds, tens, ones):
    if hundreds == '0':
        return _handle1to99(tens, ones)
    else:
        return _1to9dict[hundreds] + ' hundred ' + _handle1to99(tens, ones)
def _handle1to99(tens, ones):
    if tens == '0': 
        return _1to9dict[ones]
    elif tens == '1':
        return _10to19dict[ones]
    else:
        return _20to90dict[tens] + ' ' + _1to9dict[ones]
def test():                                                        #G
    values = sys.stdin.read().split()
    for val in values:
        print("{0} = {1}".format(val, num2words(val)))
def main():
    parser = argparse.ArgumentParser(usage=__doc__)
    parser.add_argument("num", nargs='*')
    parser.add_argument("-t", "--test", dest="test",
                      action='store_true', default=False,
                      help="Test mode: reads from stdin")
    args = parser.parse_args()
    if args.test:                                              #H
        test()
    else:
        try:
            result = num2words(args.num[0]) 
        except KeyError:                                            #J
            parser.error('argument contains non-digits')
        else: 
            print("For {0}, say: {1}".format(args.num[0], result))
if __name__ == '__main__': 
    main()                                                               #1
else:                                     
    print("n2w  loaded as a module")