Roman numerals in python

romans.py

#!/usr/bin/env python
# encoding: utf-8
"""
romans.py

Convert integer to roman numerals back and forth 
Created by Miguel Fernández on 2013-10-06.
"""

class Romans:	
	@classmethod
	def int(klass, roman):
		return RomanToIntConverter(roman).convert()
	
	@classmethod	
	def roman(klass, int):
		return IntToRomanConverter(int).convert()
		
		
class IntRomanConverter:
	
	UNITS 		= ['IX', 'VIII', 'VII', 'VI', 'V', 'IV', 'III', 'II', 'I']
	TENS 		= ['XC', 'LXXX', 'LXX', 'LX', 'L', 'XL', 'XXX', 'XX', 'X']
	HUNDREDS 	= ["CM","DCCC","DCC","DC","D","CD","CCC","CC","C"]
	THOUSANDS 	= ["MMM","MM","M"]
	
	def __init__(self, source):
		self.source = source
		
	def convert(self):
		target = self.__emptyTarget()
		rest = self.source
		(rest, target) = self.__convertUnits(rest, target, self.THOUSANDS, 1000)
		(rest, target) = self.__convertUnits(rest, target, self.HUNDREDS, 100)
		(rest, target) = self.__convertUnits(rest, target, self.TENS, 10)
		(rest, target) = self.__convertUnits(rest, target, self.UNITS, 1)
		if (not self.__isValid(rest)):
			self.__raiseError(self.source)
		return target			
		
class IntToRomanConverter(IntRomanConverter):
	
	def __emptyTarget(self):
		return ""
		
	def __isValid(self, rest):
		return rest == 0
		
	def __raiseError(self, source):
		raise Exception("Error: %d cannot be expressed as a roman" % source)
		
	def __convertUnits(self, source, target, units, unitValue):		
		if (source > 0):
			value = source / unitValue
			index = len(units) - value
			if (index >= 0 and index < len(units)):
				romanChunk = units[index]
				target += romanChunk
				source -= value * unitValue
		return (source, target)				
		
class RomanToIntConverter(IntRomanConverter):

	def __emptyTarget(self):
		return 0
		
	def __isValid(self, rest):
		return len(rest) == 0
		
	def __raiseError(self, source):
		raise Exception("Error: %s cannot be expressed as an integer" % source)
				
	def __convertUnits(self, source, target, units, unitValue):
		for index, unit in enumerate(units):
			if source.startswith(unit):
				value = (len(units) - index) * unitValue		
				return (source.replace(unit,""), target + value)
		return (source, target)

romans_test.py

#!/usr/bin/env python
# encoding: utf-8
"""
romans_test.py

Tests Romans
Created by Miguel Fernández on 2013-10-06.
"""

from romans import Romans
import unittest

class RomanToInt(unittest.TestCase):
		
	def testOne(self):
		self.assertEquals(1, Romans.int("I"))
		
	def testTwo(self):
		self.assertEquals(2, Romans.int("II"))
		
	def testFour(self):
		self.assertEquals(4, Romans.int("IV"))
		
	def testEight(self):
		self.assertEquals(8, Romans.int("VIII"))
    
	def testTen(self):
		self.assertEquals(10, Romans.int("X"))
		
	def testFifty(self):
		self.assertEquals(50, Romans.int("L"))
		
	def testSixtyNine(self):
		self.assertEquals(69, Romans.int("LXIX"))
		
	def testNinetyNine(self):
		self.assertEquals(99, Romans.int("XCIX"))
		
	def testOneHundred(self):
		self.assertEquals(100, Romans.int("C"))
		
	def testFiveHundred(self):
		self.assertEquals(500, Romans.int("D"))
		
	def testNineHundred(self):
		self.assertEquals(999, Romans.int("CMXCIX"))
		
	def testThreeThousand(self):
		self.assertEquals(3000, Romans.int("MMM"))
		
	def testThreeThousandAndOne(self):
		self.assertEquals(3001, Romans.int("MMMI"))
		
	def testThreeThousandAndSixtyNine(self):
		self.assertEquals(3069, Romans.int("MMMLXIX"))
		
class IntoToRoman(unittest.TestCase):

	def testOne(self):
		self.assertEquals("I", Romans.roman(1))
		
	def testNine(self):
		self.assertEquals("IX", Romans.roman(9))
		
	def testTen(self):
		self.assertEquals("X", Romans.roman(10))
		
	def testOneThousandAndNine(self):
		self.assertEquals("MIX", Romans.roman(1009))

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