Python - Roman Numeral to Number Generator

# Convert a roman numeral to a number. 
# 
# If you are interested in roman numerals check out my other post  
# python script that takes a number and generates a roman numeral 
# 
# For a life time of knowledge checkout: 
# http://en.wikipedia.org/wiki/Roman_numerals 
# 
 
 
 
def ConvertRomanNumeralToNumber(roman_numeral):
    number_result = 0
    
    roman_numerals = {
        1:"I", 4:"IV", 5:"V", 9:"IX",
        10:"X", 40:"XL", 50:"L",
        90:"XC", 100:"C", 400:"CD",
        500:"D", 900:"CM", 1000:"M"}
 
    # Iterate through the roman numerals.  But you see here that I sort them to 
    # get the largest string size first: "CD" comes before "I" 
    for numeral_value in sorted(roman_numerals,
                                key=lambda roman: len(roman_numerals[roman]),
                                reverse=True):
        keep_converting = True
        while keep_converting:            
            if roman_numeral.find(roman_numerals[numeral_value]) != -1:
                number_result += numeral_value
                roman_numeral = roman_numeral.replace(roman_numerals[numeral_value], "", 1)
            else:
                keep_converting = False
                
    return number_result
 
 
print(ConvertRomanNumeralToNumber("MCDXLIV"))
print(ConvertRomanNumeralToNumber("MMMDCCCLXXXVIII"))
print(ConvertRomanNumeralToNumber("MMMCMXCIX"))
 
# my output: 
#  1444 
#  3888 
#  3999