problem_17.py

#!/usr/bin/env python
import re
import sys
import unittest


NUMBERS = {
    1: 'one',
    2: 'two',
    3: 'three',
    4: 'four',
    5: 'five',
    6: 'six',
    7: 'seven',
    8: 'eight',
    9: 'nine',
    10: 'ten',
    11: 'eleven',
    12: 'twelve',
    13: 'thirteen',
    14: 'fourteen',
    15: 'fifteen',
    16: 'sixteen',
    17: 'seventeen',
    18: 'eighteen',
    19: 'nineteen',
    20: 'twenty',
    30: 'thirty',
    40: 'forty',
    50: 'fifty',
    60: 'sixty',
    70: 'seventy',
    80: 'eighty',
    90: 'ninety'

}


get_first_digit = lambda number: int(str(number)[0])
get_rest = lambda number: int(str(number)[1:])
s_if_plural = lambda first_digit, use_plural: 's' if use_plural and first_digit > 1 else ''

ten = '{0}-{1}'
hundred = '{0} hundred{1}'
hundred_remainder = '{0} and {1}'
thousand = '{0} thousand{1}'
thousand_remainder = '{0} {1}'


def get_number_name(number, use_plural=False):

    first_digit = get_first_digit(number)

    if number in NUMBERS:
        return NUMBERS[number]

    elif 100 > number > 20:
        return ten.format(
            get_number_name(first_digit * 10, use_plural),
            get_number_name(get_rest(number), use_plural)
        )

    elif int(1e3) > number >= 100:

        if not (number % 100):
            return hundred.format(
                get_number_name(first_digit, use_plural),
                s_if_plural(first_digit, use_plural)
            )

        else:
            return hundred_remainder.format(
                get_number_name(first_digit * 100, use_plural),
                get_number_name(get_rest(number), use_plural)
            )

    elif int(1e6) > number >= int(1e3):

        if not (number % int(1e3)):
            return thousand.format(
                get_number_name(first_digit, use_plural),
                s_if_plural(first_digit, use_plural)
            )

        else:
            return thousand_remainder.format(
                get_number_name(first_digit * int(1e3), use_plural),
                get_number_name(get_rest(number), use_plural)
            )


def get_letter_count(number, use_plural=False):
    number_name = get_number_name(number, use_plural)
    return len(re.sub(r'[- ]', '', number_name))


def get_number_letter_counts(start, end, use_plural=False):
    return sum(get_letter_count(x, use_plural) for x in range(start, end + 1))


class TestHelpers(unittest.TestCase):

    def test_get_letter_count(self):
        self.assertEqual(get_letter_count(342), 23)
        self.assertEqual(get_letter_count(342, use_plural=True), 24)
        self.assertEqual(get_letter_count(115), 20)

    def test_get_number_letter_counts(self):
        self.assertEqual(get_number_letter_counts(1, 5), 19)


if __name__ == '__main__':
    if len(sys.argv) == 2 and sys.argv[1] == 'test':
        sys.argv.pop()
        unittest.main()
    else:
        result = get_number_letter_counts(1, 1000)
        print(result)