Scripting languages homework

roman.py

#!/usr/bin/env python

def to_roman(num):
    # is input between 0 and 4000?
    if not 0 < int(num) < 4000: return False

    length = len(num)
    res = ''
    for s in num:
        # get dictionary for current word length
        romans_dict = get_dictionary(length)
        if not romans_dict: return False

        # sort dictionary keys
        romans_keys = romans_dict.keys()
        romans_keys.sort()

        numeral = int(s)
        rom = ''

        if numeral <= 3: # 0 - 3
            rom = romans_dict[1] * numeral
        elif numeral <= 8: # 4 - 8
            if (numeral - 5) < 0:
                rom = romans_dict[1] * abs(numeral - 5)
                rom += romans_dict[5]
            else:
                rom = romans_dict[5]
                rom += romans_dict[1] * (numeral - 5)
        else: # 9
            rom = romans_dict[1] + romans_dict[10]

        res += rom
        length -= 1

    return res

def get_dictionary(length):
    # is input between 1 and 5?
    if not 0 < length < 5: return False

    if length == 1:   return {1:'I', 5: 'V', 10:'X'}
    elif length == 2: return {1:'X', 5:'L', 10:'C'}
    elif length == 3: return {1:'C', 5:'D', 10:'M'}
    else: return {1:'M',}

roman.test.py

#!/usr/bin/env python

""" Unit tests for roman converter """

import roman
import unittest

class ToRomanKnownValues(unittest.TestCase):
    knownValues = ( (1, 'I'),
                    (2, 'II'),
                    (3, 'III'),
                    (4, 'IV'),
                    (5, 'V'),
                    (6, 'VI'),
                    (7, 'VII'),
                    (8, 'VIII'),
                    (9, 'IX'),
                    (10, 'X'),
                    (11, 'XI'),
                    (12, 'XII'),
                    (13, 'XIII'),
                    (14, 'XIV'),
                    (15, 'XV'),
                    (100, 'C'),
                    (101, 'CI') )

    def testKnownValues(self):
        for integer, numeral in self.knownValues:
            result = roman.to_roman(str(integer))
            self.assertEquals(numeral, result)

    def testBorders(self):
        self.assertFalse(roman.to_roman(0))
        self.assertFalse(roman.to_roman(4000))


class GetDictionary(unittest.TestCase):
    def testKnownValues(self):
        dictionary = roman.get_dictionary(1)
        self.assertEquals('X', dictionary[10])

        dictionary = roman.get_dictionary(2)
        self.assertEquals('C', dictionary[10])

        dictionary = roman.get_dictionary(3)
        self.assertEquals('M', dictionary[10])

        dictionary = roman.get_dictionary(4)
        self.assertEquals('M', dictionary[1])

    def testBorders(self):
        dictionary = roman.get_dictionary(0)
        self.assertFalse(dictionary)

        dictionary = roman.get_dictionary(5)
        self.assertFalse(dictionary)

if __name__ == "__main__":
    unittest.main()