new_contents: class Solution:
      # @param n, an integer
      # @return, an integer
      def reverseBits(self, n):
          n_bin = bin(n)[-1: 1: -1] # remove '0b' of the bin string and reverse it
          n_reversed = n_bin + (32 - len(n_bin)) * '0' # append 0 if not 32 bit
          return int(n_reversed, base=2)
  
  if __name__ == '__main__':
      s = Solution()
      print s.reverseBits(43261596)
  
subject: add reverse bits