I’ve build a Roman numeral class in python, and I want to know what can be improved in it. An assumption I’m making is that the initialization of an object will use valid roman numerals (I, V, X, L, C, D, M).
class RomanNumeral: def __init__(self, roman_numeral=''): self.roman_numeral = roman_numeral.upper() self.value = 0 # arabic value self.simple_form = '' # Least possible number of character equivalence of Roman numeral self.valid = False # Is the Roman numeral valid self.arabs = [] # List of corresponding arabic numbers self.convert = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000} self.reverse_convert = dict((v, k) for k, v in self.convert.items()) self.reverse_convert.update({4: 'IV', 9: 'IX', 40: 'XL', 90: 'XC', 400: 'CD', 900: 'CM'}) self.convert_arabs() self.convert_value() self.convert_simple() def __repr__(self): return self.roman_numeral def __str__(self): return f'{self.roman_numeral} : {self.value}' def convert_arabs(self): """ Converts the roman numeral to a list of the corresponding arabic numbers for each roman numeral """ self.arabs = [] for i, num in enumerate(self.roman_numeral): if num == 'I' and i != len(self.roman_numeral) - 1: if self.roman_numeral[i+1] == 'V': self.arabs.append(4) continue elif self.roman_numeral[i+1] == 'X': self.arabs.append(9) continue if num == 'X' and i != len(self.roman_numeral) - 1: if self.roman_numeral[i+1] == 'L': self.arabs.append(40) continue elif self.roman_numeral[i+1] == 'C': self.arabs.append(90) continue if num == 'C' and i != len(self.roman_numeral) - 1: if self.roman_numeral[i+1] == 'D': self.arabs.append(400) continue elif self.roman_numeral[i+1] == 'M': self.arabs.append(900) continue if num == 'V' and i != 0 and self.roman_numeral[i-1] == 'I': continue if num == 'X' and i != 0 and self.roman_numeral[i-1] == 'I': continue if num == 'L' and i != 0 and self.roman_numeral[i-1] == 'X': continue if num == 'C' and i != 0 and self.roman_numeral[i-1] == 'X': continue if num == 'D' and i != 0 and self.roman_numeral[i-1] == 'C': continue if num == 'M' and i != 0 and self.roman_numeral[i-1] == 'C': continue self.arabs.append(self.convert[num]) def is_valid(self): """ Checks if the Roman Numeral is valid """ desc_sort = self.arabs == sorted(self.arabs)[::-1] # Numerals must be in descending order small_exceed = True # Cannot have number of smaller values exceed X, C, or M if self.roman_numeral.count('I') > 9: small_exceed = False if self.roman_numeral.count('X') > 9: small_exceed = False if self.roman_numeral.count('C') > 9: small_exceed = False five_once = True # Cannot have more than one V, L, D if self.roman_numeral.count('V') > 1: five_once = False if self.roman_numeral.count('L') > 1: five_once = False if self.roman_numeral.count('D') > 1: five_once = False return desc_sort and small_exceed and five_once def convert_value(self): """ Convert the value of the roman numeral to the arabic number """ self.value = sum(self.arabs) def convert_simple(self): """ Converts the roman numeral to its simplest form, meaning the least number of characters """ subtract_list = sorted(self.reverse_convert.keys())[::-1] simplel = [] curr_val = self.value i = 0 while curr_val > 0: if curr_val - subtract_list[i] >= 0: simplel.append(subtract_list[i]) curr_val -= subtract_list[i] else: i = (i + 1) % len(subtract_list) # Go back to beginning self.simple_form = ''.join(self.reverse_convert[i] for i in simplel) # make into simplest form 
