Using Python to parse roman numerals using Regex -


this question has answer here:

i need convert roman numeral string integer. have no clue how start, need use regex.

import re  def romannumeraltoint(romannum):     romannum = romannum.upper()     totalvalue = 0

i have series of tests should past:

def test():     print("tests started.")     x = "iii"     "" if romannumeraltoint(x) == 3 else print(x + " - " + str(romannumeraltoint(x)))     x = "iv"     "" if romannumeraltoint(x) == 4 else print(x + " - " + str(romannumeraltoint(x)))     x = "ix"     "" if romannumeraltoint(x) == 9 else print(x + " - " + str(romannumeraltoint(x)))     x = "c"     "" if romannumeraltoint(x) == 100 else print(x + " - " + str(romannumeraltoint(x)))     x = "cc"     "" if romannumeraltoint(x) == 200 else print(x + " - " + str(romannumeraltoint(x)))     x = "ccc"     "" if romannumeraltoint(x) == 300 else print(x + " - " + str(romannumeraltoint(x)))     x = "cd"     "" if romannumeraltoint(x) == 400 else print(x + " - " + str(romannumeraltoint(x)))     x = "d"     "" if romannumeraltoint(x) == 500 else print(x + " - " + str(romannumeraltoint(x)))     x = "dc"     "" if romannumeraltoint(x) == 600 else print(x + " - " + str(romannumeraltoint(x)))     x = "dcc"     "" if romannumeraltoint(x) == 700 else print(x + " - " + str(romannumeraltoint(x)))     x = "dccc"     "" if romannumeraltoint(x) == 800 else print(x + " - " + str(romannumeraltoint(x)))     x = "m"     "" if romannumeraltoint(x) == 1000 else print(x + " - " + str(romannumeraltoint(x)))     x = "lxi"     "" if romannumeraltoint(x) == 61 else print(x + " - " + str(romannumeraltoint(x)))     x = "ic"     "" if romannumeraltoint(x) == 99 else print(x + " - " + str(romannumeraltoint(x)))     x = "mmci"     "" if romannumeraltoint(x) == 2101 else print(x + " - " + str(romannumeraltoint(x)))     print("tests ended.")

you can use regex split string ccmmi 3 parts: string of largest value ("mm"), whatever's left of subtracted, , whatever's right of added.

you have trivial problem of finding value of string of single value (mm), , 2 smaller problems of finding value of 2 roman numerals don't include "m" (cc , i). can divide , conquer until base case of empty string, 0.

here's suboptimal implementation of this, lot more matching necessary , has no input validation (wouldn't want ruin fun):

import re  values = [ ("m", 1000), ("d", 500), ("c", 100),     ("l", 50), ("x", 10), ("v", 5), ("i", 1) ]  def romannumeraltoint(romannum):     (c, v) in values:         match = re.match("(.*?)(" + c + "+)(.*)", romannum)            if match:                                                       return len(match.group(2)) * v \                 - romannumeraltoint(match.group(1)) \                 + romannumeraltoint(match.group(3))     return 0

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