Check if an input is a valid roman numeral

Question

I got a program that converts Roman numerals to integers and vice versa. My problem is that I don´t really know how to create a function that checks if the user input is a v

Answer 1

Instead of looping, you can convert both input and valid literals to sets and then substract them:

def checkIfRomanNumeral(numeral):
    numeral = {c for c in numeral.upper()}
    validRomanNumerals = {c for c in "MDCLXVI()"}
    return not numeral - validRomanNumerals

Returns True if numeral is valid, False otherwise. (Assuming that the empty string is valid)