def number_to_numeral(n):
    """
    returns minimal numeral
    """
    remainder = n
    values = [1000, 500, 100, 50, 10, 5, 1]
    substractive_cases = [None, 100, 100, 10, 10, 1, 1]
    symbols = dict(zip(values, ['M', 'D', 'C', 'L', 'X', 'V', 'I']))
    numeral = ''
    for i in range(len(values)):
        if remainder >= values[i]:
            # first substractive test
            if substractive_cases[i] != None and i > 0:
                if (remainder + substractive_cases[i]) >= values[i-1]:
                    remainder -= (values[i-1] - substractive_cases[i])
                    numeral += symbols[substractive_cases[i]] + symbols[values[i-1]]
            # then normal test
            while remainder >= values[i]:
                remainder -= values[i]
                numeral += symbols[values[i]]
    return numeral

for i in range(1, 21):
    print(number_to_numeral(i))

number_to_numeral(9)

number_to_numeral(19)

number_to_numeral(400)

number_to_numeral(405)

number_to_numeral(900)

number_to_numeral(1900)

def numeral_to_number(numeral):
    number = 0
    values = [1000, 500, 100, 50, 10, 5, 1]
    symbols = dict(zip(['M', 'D', 'C', 'L', 'X', 'V', 'I'], values))
    for ind, num in enumerate(numeral):
        if not ind == len(numeral) - 1:
            if symbols[numeral[ind+1]] > symbols[num]:
                number -= symbols[num]
            else:
                number += symbols[num]
        else:
            number += symbols[num]
    return number

numeral_to_number('MMMDLXVIIII')

number_to_numeral(3569)

import urllib2  # the lib that handles the url stuff
data = urllib2.urlopen("https://projecteuler.net/project/resources/p089_roman.txt").readlines() # it's a file like object and works just like a file

initial_lengths = []
shortest_lengths = []
for line in data: # files are iterable
    initial_lengths.append(len(line.strip()))
    n = numeral_to_number(line.strip())
    shortest_lengths.append(len(number_to_numeral(n)))

sum(initial_lengths)

sum(shortest_lengths)

sum(initial_lengths) - sum(shortest_lengths)