Simple Python function to convert an integer to a Roman number.

roman_number.py

def numberToRoman(numVal, isLower=False):
    """Convert an integer to a roman number.
    """
    if not isinstance(numVal, int):
        return "NAN"
    if numVal < 1 or numVal > 4999:
        return "OOR"

    theValues = [
        (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"),
    ]

    romNum = ""
    for theDiv, theSym in theValues:
        n = numVal//theDiv
        romNum += n*theSym
        numVal -= n*theDiv
        if numVal <= 0:
            break

    return romNum.lower() if isLower else romNum