code: def calcMD5(path):
      
      # check that file exists
      if os.path.exists(path) is False:
          yield False
      else:
          command = ['md5sum', path]
          p = Popen(command, stdout = PIPE)
          for line in p.communicate()[0].splitlines():
              yield line.decode('ascii').strip().split()[0]
          p.wait()
          yield False
docs: calc MD5 based on path