***Help! Code not working out-Roman Numeral Converter

[tech12]

This is a project I'm working on for a class. I'm pretty new to CS and python...and I found that I am totally lost. I'm suppose to write a program to convert Roman numerals to arabic numbers. It is also suppose to handle invalid input.

Here is what I have so far:

def roman_converter():

R=str.upper(raw_input("Enter a Roman numeral to convert to Arabic: "))

d={'I':1, 'V':5, 'X':10, 'L':50, 'C':100, 'D':500, 'M':1000}

s=0
for c in range(len(R)):
while R[0]

[alc6379]

Well, there's two types of validation... you'll need to first verify that the numerals are in the right order, ie, you can't have IC or something, but you could have XC, or IX, but not VX or IL, etc. That's one validation.

The other validation that you would need is to make sure that ONLY characters used for roman numerals are input. If you're just working with I,V,X,L,C,D,and M, then any other character is invalid.

Does that make sense?

[woooee]

You might start with code tags (use the "#" icon) and then explain what the program you posted does, as it doesn't appear to make sense. Once you reach this line
while R[0]