new_contents: class Solution(object):
      def addStrings(self, num1, num2):
          """
          :type num1: str
          :type num2: str
          :rtype: str
          """
          result = ''
          carry  = 0
          
          digs1  = num1.zfill(len(num2))[::-1]
          digs2  = num2.zfill(len(num1))[::-1]
      
          for dig1, dig2 in zip(digs1, digs2):
              add     = carry + sum(map(int, (dig1, dig2)))
              resdig  = str(add % 10)
              carry   = add // 10
                  
              result += resdig
                  
          if carry > 0:
              result += str(carry)
                  
          return result[::-1]
  
subject: Create solution.py