#! /usr/bin/env python3.1
"""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, optparse
# conversion mappings
_1to9dict = {'0': '', '1': 'one', '2': 'two', '3': 'three', '4': 'four',
             '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"""
    # handle the special conditions (number is zero or too large)
    if num_string == '0': 
        return'zero'
    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)
    # working from least to most significant digit creates a string 
    # containing the number
    num_string = '00' + num_string            # pad the number on the left
    word_string = ''                          # initiate string for number
    for mag, name in _magnitude_list:
        if mag >= num_length: 
            return word_string
        else: 
            hundreds, tens, ones = num_string[-mag-3], \
                 num_string[-mag-2], num_string[-mag-1]
            if not (hundreds == tens == ones == '0'):
                 word_string = _handle1to999(hundreds, tens, ones) + \
                                             name + word_string
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():
    values = sys.stdin.read().split()
    for val in values:
        num  = val.replace(',', '')
        print("{0} = {1}".format(val, num2words(num)))
def main():
    parser = optparse.OptionParser(usage=__doc__)
    parser.add_option("-t", "--test", dest="test",
                      action='store_true', default=False, 
                      help="Test mode: reads from stdin")
    (options, args) = parser.parse_args()
    if options.test:
        test()
    else:
        if len(args) < 1:
            parser.error("incorrect number of arguments")
        num = sys.argv[1].replace(',', '')
        try:
            result = num2words(num) 
        except KeyError:
            parser.error('argument contains non-digits')   
        else: 
            print("For {0}, say: {1}".format(sys.argv[1], result))
if __name__ == '__main__': 
    main()
else:                                     
    print("n2w  loaded as a module")