LeetCode - Roman to Integer conversion

Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
Input format is ‘String’

Example:
Sample Input: ‘XXVII’
Output : 27

#!/bin/python
#num is input Roman number
def romanToInt(self, num):
        dic = {'I': 1, 'V': 5, 'X': 10, 'L':50, 'C':100, 'D': 500, 'M': 1000}
        l = len(num)
        integer = dic[num[l-1]]
        for i in range(l-1,0,-1):
            if dic[num[i]] <= dic[num[i-1]]:
                integer += dic[num[i-1]]
            else:
                integer -= dic[num[i-1]]
        return integer