Basic program to convert integer to Roman numerals?

Question

I'm trying to write a code that converts a user-inputted integer into its Roman numeral equivalent. What I have so far is:

The point of the generate_all_of_numeral function is so that it creates a string for each specific numeral. For example, generate_all_of_numeral(2400, 'M', 2000) would return the string 'MM'.

I'm struggling with the main program. I start off finding the Roman numeral count for M and saving that into the variable M. Then I subtract by the number of M's times the symbol value to give me the next value to work with for the next largest numeral.

Any nod to the right direction? Right now my code doesn't even print anything.

Answer 1

A KISS version of Manhattan's algorithm, without any "advanced" notion such as OrderedDict, recursion, generators, inner function and break:

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"),
]

def int_to_roman(number):
    result = ""
    for (arabic, roman) in ROMAN:
        (factor, number) = divmod(number, arabic)
        result += roman * factor
    return result

An early exit could be added as soon as number reaches zero, and the string accumulation could be made more pythonic, but my goal here was to produce the requested basic program.

Tested on all integers from 1 to 100000, which ought to be enough for anybody.

EDIT: the slightly more pythonic and faster version I alluded to:

def int_to_roman(number):
    result = []
    for (arabic, roman) in ROMAN:
        (factor, number) = divmod(number, arabic)
        result.append(roman * factor)
        if number == 0:
            break
    return "".join(result)

Answer 2

Here's what I tried:

def int_to_roman(num):
    dict_of_known_val = {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'}
    result = ''
    for key, value in dict_of_known_val.items():
        x, y = divmod(num, key)
        result += value * x
        num = y
    return result

This code works for me.