Update roman_numerals.py

Reduced lines of code, time complexity , reduced error matrix. 
Increased options for the user

conversions/roman_numerals.py

@@ -1,61 +1,28 @@
-ROMAN = [
-    (1000, "M"),
-    (900, "CM"),
-    (500, "D"),
-    (400, "CD"),
-    (100, "C"),
-    (90, "XC"),
-    (50, "L"),
-    (40, "XL"),
-    (10, "X"),
-    (9, "IX"),
-    (5, "V"),
-    (4, "IV"),
-    (1, "I"),
-]
+ROMAN_NUMERALS = {
+    1000: "M", 900: "CM", 500: "D", 400: "CD", 100: "C",
+    90: "XC", 50: "L", 40: "XL", 10: "X", 9: "IX", 5: "V", 4: "IV", 1: "I"
+}
 
-
-def roman_to_int(roman: str) -> int:
-    """
-    LeetCode No. 13 Roman to Integer
-    Given a roman numeral, convert it to an integer.
-    Input is guaranteed to be within the range from 1 to 3999.
-    https://en.wikipedia.org/wiki/Roman_numerals
-    >>> tests = {"III": 3, "CLIV": 154, "MIX": 1009, "MMD": 2500, "MMMCMXCIX": 3999}
-    >>> all(roman_to_int(key) == value for key, value in tests.items())
-    True
-    """
-    vals = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}
-    total = 0
-    place = 0
-    while place < len(roman):
-        if (place + 1 < len(roman)) and (vals[roman[place]] < vals[roman[place + 1]]):
-            total += vals[roman[place + 1]] - vals[roman[place]]
-            place += 2
+def roman_to_int(roman):
+    result = 0
+    i = 0
+    while i < len(roman):
+        if i + 1 < len(roman) and roman[i:i+2] in ROMAN_NUMERALS:
+            result += ROMAN_NUMERALS[roman[i:i+2]]
+            i += 2
         else:
-            total += vals[roman[place]]
-            place += 1
-    return total
-
-
-def int_to_roman(number: int) -> str:
-    """
-    Given a integer, convert it to an roman numeral.
-    https://en.wikipedia.org/wiki/Roman_numerals
-    >>> tests = {"III": 3, "CLIV": 154, "MIX": 1009, "MMD": 2500, "MMMCMXCIX": 3999}
-    >>> all(int_to_roman(value) == key for key, value in tests.items())
-    True
-    """
-    result = []
-    for arabic, roman in ROMAN:
-        (factor, number) = divmod(number, arabic)
-        result.append(roman * factor)
-        if number == 0:
-            break
-    return "".join(result)
+            result += ROMAN_NUMERALS[roman[i]]
+            i += 1
+    return result
 
+def int_to_roman(number):
+    result = ""
+    for value, numeral in ROMAN_NUMERALS.items():
+        while number >= value:
+            result += numeral
+            number -= value
+    return result
 
 if __name__ == "__main__":
     import doctest
-
     doctest.testmod()