leetcode 166. Fraction to Recurring Decimal

class Solution(object):    def fractionToDecimal(self, numerator, denominator):        res = ""        if(numerator * denominator < 0):            res += "-"        numerator = abs(numerator)        denominator = abs(denominator)        quotient = numerator//denominator        res += str(quotient)        numerator -= quotient*denominator        num_set = {}        if(numerator == 0):            return res        else:            res += "."        num_set[numerator] = len(res)        while(numerator):            numerator *= 10            quotient = numerator//denominator            res += str(quotient)            numerator -= quotient*denominator            if(numerator in num_set):                res = res[:num_set[numerator]]+"("+res[num_set[numerator]:]                res += ')'                break;            num_set[numerator] = len(res)        return res