- added support for 0 / N

see https://en.wikipedia.org/wiki/Roman_numerals#Zero

CHANGES.txt

@@ -5,6 +5,9 @@ CHANGES
 3.2 (unreleased)
 ----------------
 
+- Added support for 0 -> N
+  (see https://en.wikipedia.org/wiki/Roman_numerals#Zero)
+
 - Added support for Python 3.8
 
 

src/roman.py

@@ -41,8 +41,12 @@ def toRoman(n):
     """convert integer to Roman numeral"""
     if not isinstance(n, int):
         raise NotIntegerError("decimals can not be converted")
-    if not (0 < n < 5000):
-        raise OutOfRangeError("number out of range (must be 1..4999)")
+    if not (-1 < n < 5000):
+        raise OutOfRangeError("number out of range (must be 0..4999)")
+
+    # special case
+    if n == 0:
+        return 'N'
 
     result = ""
     for numeral, integer in romanNumeralMap:
@@ -68,6 +72,11 @@ def fromRoman(s):
     """convert Roman numeral to integer"""
     if not s:
         raise InvalidRomanNumeralError('Input can not be blank')
+
+    # special case
+    if s == 'N':
+        return 0
+
     if not romanNumeralPattern.search(s):
         raise InvalidRomanNumeralError('Invalid Roman numeral: %s' % s)
 

src/tests.py

@@ -4,6 +4,7 @@
 class TestRoman(unittest.TestCase):
 
     def test_toRoman(self):
+        self.assertEqual(roman.toRoman(0), 'N')
         self.assertEqual(roman.toRoman(1), 'I')
         self.assertEqual(roman.toRoman(2013), 'MMXIII')
 
@@ -12,6 +13,7 @@ def test_toRoman_errors(self):
         self.assertRaises(roman.NotIntegerError, roman.toRoman, '1')
 
     def test_fromRoman(self):
+        self.assertEqual(roman.fromRoman('N'), 0)
         self.assertEqual(roman.fromRoman('I'), 1)
         self.assertEqual(roman.fromRoman('MMXIII'), 2013)