new_contents: class Solution:
      def hammingWeight(self, n):
          n_bin = bin(n)
          count = 0
          for i in n_bin[1:]:
              if i == '1':
                  count += 1
          return count
  
  
  if __name__ == '__main__':
      s = Solution()
      print s.hammingWeight(11)
  
subject: add numer of 1 bits