Roman numerals (Roman numbers) to integer (concisely in Python)

roman_to_int.py

def roman_to_int(roman_string):
    
    symbol_groups = [{'IV': 4, 'IX': 9, 'XL': 40, 'XC': 90, 'CD': 400, 'CM': 900},
                     {'M': 1000,'D': 500 ,'C': 100,'L': 50,'X': 10,'V': 5,'I': 1}]
    
    result = 0 # initially
    for symbol_group in symbol_groups:
        for symbol, value in symbol_group.items():
            result += roman_string.count(symbol) * value
            roman_string = roman_string.replace(symbol, '')
    return result