Sample solution for converting roman numerals to integers

roman.py

def convert(char):
	return {
		'M': 1000,
		'D': 500,
		'C': 100,
		'L': 50,
		'X': 10,
		'V': 5,
		'I': 1
	}.get(char)

def romanToInteger(input):
	# Turns each character of the input into an integer
	# e.g. "IV" becomes [1, 5] after this
	converted = map(convert, list(input))
	
	# Call the helper function with the converted list,
	# and a starting sum of 0
	return _romanToInteger(converted, 0)

def _romanToInteger(input, lastSum):
	# If there are no characters left, we are done, so return the last sum
	if len(input) == 0:
		return lastSum
		
	# If there are at least two characters left, and the first character
	# is smaller than the second character, then subtract the first from
	# the second, add the result to lastSum, and recurse on the remainder
	# of the input
	elif len(input) > 1 and input[0] < input[1]:
		return _romanToInteger(input[2:], lastSum + input[1] - input[0])
		
	# Otherwise, add the first character of the input, and recurse on
	# the remainder of the input
	else:
		return _romanToInteger(input[1:], lastSum + input[0])

print(romanToInteger('IV'))
print(romanToInteger('X'))
print(romanToInteger('XVI'))
print(romanToInteger('DC'))
print(romanToInteger('MCD'))